diff --git a/MODS.md b/MODS.md
index 1a2038d..a4ec82b 100644
--- a/MODS.md
+++ b/MODS.md
@@ -394,6 +394,7 @@ interface ServerContext {
 	world: ServerWorld;
 	players: PlayerList;
 	containers: ContainerApi;
+	items: ItemApi;
 	recipes: RecipeApi;
 	ui: ServerUi; // see GUIs
 	net: ServerNet; // see Mod channels
@@ -477,6 +478,7 @@ interface ServerWorld {
 	get_state(x: number, y: number, z: number, name: string): number | undefined;
 	set_state(x: number, y: number, z: number, name: string, value: number): boolean;
 	get_block_data<T>(x: number, y: number, z: number): T | undefined;
+	drop_item(x: number, y: number, z: number, item: ItemStack): void; // pops out of the block, like drops
 	is_loaded(x: number, z: number): boolean;
 	readonly seed: string;
 }
@@ -612,8 +614,8 @@ code sees it.
 ### 2. Container screens (server only)
 
 For inventories and machines. The server owns the container's contents and syncs them to every player viewing it. Clicks
-go to the server, which applies them. The chest and furnace would be rebuilt this way instead of their hand-written
-`GuiChest` / `GuiFurnace` classes.
+go to the server, which applies them. The base game's chest and furnace are built this way, see
+`mods/bworld/scripts/server.ts`.
 
 ```ts
 ctx.components.register_block("copper_tools:smelter", {
@@ -623,36 +625,50 @@ ctx.components.register_block("copper_tools:smelter", {
 	on_interact(block, _params, player) {
 		const container = ctx.containers.get(block.data.container)!;
 		const screen = ctx.ui.open_container(player, {
-			title: "Smelter",
+			container,
 			layout: [
 				{ slot: 0, x: 3, y: 0, filter: "smeltable" },
 				{ slot: 1, x: 3, y: 2, filter: (item) => ctx.recipes.is_fuel(item.id) },
 				{ slot: 2, x: 5, y: 1, output_only: true },
 			],
-			container,
-			player_inventory: true,
-			bars: [{ id: "progress", x: 4, y: 1, texture: "bworld:arrow" }],
+			bars: [{
+				x: 4,
+				y: 1,
+				value: "progress",
+				max: "progress_max",
+				direction: "right",
+				empty_texture: "bworld:arrow_empty",
+				full_texture: "bworld:arrow_full",
+			}],
 		});
 		screen.set_property("progress", block.data.progress);
+		screen.set_property("progress_max", 200);
 		return true;
 	},
+	on_break(block) {
+		ctx.containers.delete(block.data.container);
+	},
 });
 ```
 
-- `x` / `y` are in slot units on a grid. The client scales and centers the screen, and draws the player's inventory
-  below it when `player_inventory` is true.
+- The screen is drawn below the player's inventory and hotbar. `x` / `y` are in slot units in the screen's own area and
+  can be fractional. `rows` sets its height, by default it fits the slots and bars.
 - `filter` is a function `(item) => boolean` or one of the built-in filters `"smeltable"` (has a furnace recipe) and
   `"fuel"`. It and `output_only` run **on the server**, so players can't put the wrong items in by editing their client.
-- `bars` are progress bars filled from 0 to 1 by `screen.set_property(id, value)`. Properties can also be shown as text
-  with `labels: [{ x, y, property }]`.
-- The screen handle has `set_property`, `close()` and `on_close(fn)`. Changes to the container (from scripts, hoppers,
+  `output_only` slots can only be taken from, all at once, like the furnace result.
+- `bars` are progress bars filled with `value / max`, both names of properties set with `screen.set_property(id, n)`.
+  `direction` is `"up"` (like the furnace's fire) or `"right"` (like its arrow). Properties are synced when they change,
+  so a component can update them every tick.
+- The screen handle has `player`, `open`, `set_property`, `close()` and `on_close(fn)`. It closes when the player closes
+  it, leaves, or opens another screen, and when its container is deleted. Changes to the container (from scripts,
   other players) show up for everyone viewing it.
+- Containers are saved with the world until they're deleted, so a block that has one deletes it in `on_break`.
 
 ```ts
 interface ContainerApi {
-	create(size: number): Container; // saved with the world
+	create(size: number): Container; // 1 to 256 slots, saved with the world
 	get(id: string): Container | undefined;
-	delete(id: string): void;
+	delete(id: string): void; // closes screens showing it
 }
 
 interface Container {
@@ -663,8 +679,15 @@ interface Container {
 	add(item: ItemStack): ItemStack | undefined; // returns what didn't fit
 	on_change(fn: (slot: number) => void): () => void;
 }
+
+interface ItemApi {
+	exists(id: string): boolean;
+	max_stack(id: string): number;
+}
 ```
 
+Items handed to scripts are live: setting `count` changes the stack, and a stack counted down to 0 is gone.
+
 ### 3. Custom screens (client code)
 
 For anything forms and containers can't do: maps, skill trees, minigames, custom layouts. The client script registers a
@@ -1036,15 +1059,21 @@ export function setup(ctx: ServerContext) {
 		on_interact(block, _params, player) {
 			const data = block.data as SmelterData;
 			ctx.ui.open_container(player, {
-				title: "Smelter",
 				container: ctx.containers.get(data.container)!,
 				layout: [
 					{ slot: 0, x: 3, y: 0, filter: "smeltable" },
 					{ slot: 1, x: 3, y: 2, filter: "fuel" },
 					{ slot: 2, x: 5, y: 1, output_only: true },
 				],
-				player_inventory: true,
-				bars: [{ id: "progress", x: 4, y: 1, texture: "bworld:arrow" }],
+				bars: [{
+					x: 4,
+					y: 1,
+					value: "progress",
+					max: "progress_max",
+					direction: "right",
+					empty_texture: "bworld:arrow_empty",
+					full_texture: "bworld:arrow_full",
+				}],
 			}).set_property("progress", data.progress);
 			return true;
 		},
@@ -1126,10 +1155,10 @@ anything the base game does.
 
 Not moved:
 
-- **Crops** (`common/blocks/crops.ts`) are unfinished and mostly commented out. They stay where they are and get rebuilt
-  as a component once server scripts exist, as a good first test of tile data plus ticking.
-- **The watering can's lore** (`get_lore`) isn't shown anywhere yet, because the game has no item tooltips. It moves
-  once tooltips exist.
+- **Carrots, potatoes, tomatoes and pumpkins** (`common/blocks/crops.ts`) are unfinished and mostly commented out.
+  Wheat uses the `bworld:crop` component instead, and they can too once they have blocks.
+- **The watering can's lore** moved into its component's `get_lore`, but it isn't shown anywhere yet, because the game
+  has no item tooltips.
 
 ### What stays in the engine
 
@@ -1150,7 +1179,8 @@ Worlds saved before the move must load afterwards with nothing changed:
 3. **Tile data keeps its shape.** Chests store their items in `containers.main`, and furnaces keep `containers.main`
    plus `progress`, `progress_max`, `fuel` and `fuel_max` in `data`. The components read exactly those, so tiles saved
    by the current code load into them.
-4. **The save format and protocol don't change.** Clients receive `mods/bworld` like any other mod.
+4. **The protocol doesn't change, and old saves load.** Clients receive `mods/bworld` like any other mod. The save
+   format may change when it has to, as long as older saves are upgraded when loading (phase 2 did, to version 3).
 
 ### Phases
 
@@ -1180,14 +1210,17 @@ loading mods (the base game and the template), their scripts and worldgen, saves
 - Delete `common/blocks/` and `common/items/`.
 - Check: the registry built from JSON equals `registry.json`, and all tests pass.
 
-**Phase 2: behavior** (after step 6, and container screens from step 7).
+**Phase 2: behavior** (after step 6, and container screens from step 7). _Done._
 
-- `mods/bworld/scripts/server.ts` registers `bworld:hoeable`, `bworld:storage`, `bworld:furnace` and
-  `bworld:watering_can`. The chest and furnace open their screens with `ctx.ui.open_container`, whose layouts are the
-  `ScreenLayout`s the server sends now.
-- The block JSON lists the components. Delete `server/game/blocks.ts`.
-- Check: the server logic tests (hoeing, chest, furnace smelting, breaking a chest gives its contents back) and
-  `world_v2.json` still pass.
+- `mods/bworld/scripts/server.ts` registers `bworld:hoeable`, `bworld:storage`, `bworld:furnace`, `bworld:crop` (bone
+  meal on wheat) and `bworld:watering_can`. The chest and furnace open their screens with `ctx.ui.open_container`, with
+  the same layouts as before.
+- The block and item JSON lists the components. `server/game/blocks.ts` is deleted.
+- Saves went to version 3: tiles only keep `mod_data`, and containers are saved by id. Version 2 chests and furnaces are
+  upgraded when loaded: their `data` fields stay and their `containers.main` becomes a container whose id is in
+  `container`, which is the shape the components use.
+- Check: `tests/base_game_test.ts` (hoeing, chest, furnace smelting, breaking a chest gives its contents back, bone meal,
+  the watering can) and `tests/fixtures/world_v2.json`, saved by the engine code before the move, pass.
 
 **Phase 3: world generation** (after step 9).
 
@@ -1239,10 +1272,11 @@ working:
    joining. Add the confirm screen for cross-origin servers and CORS headers on the server. _Done._
 6. **Server scripts.** Components, events, commands, system, storage and `ctx.recipes`. Move `FURNACE_RECIPES` and
    `FUEL_VALUES` into the recipe registry. _Done_ (`server/game/mod_runtime.ts`, with the loop in
-   `server/game/game_loop.ts`). `ctx.containers`, `ctx.ui` and `ctx.net` throw until steps 7 and 8, and so do the
-   client's `ctx.ui`, `ctx.hud`, `ctx.input` and `ctx.net`.
+   `server/game/game_loop.ts`). `ctx.net` throws until step 8, and so do the client's `ctx.ui`, `ctx.hud`,
+   `ctx.input` and `ctx.net`.
 7. **GUIs.** Forms, then container screens (rebuild chest and furnace with them), then custom screens, the `Graphics`
-   API (built on the existing renderer and debug UI widgets) and the HUD.
+   API (built on the existing renderer and debug UI widgets) and the HUD. _Container screens done_ (`ctx.containers`,
+   `ctx.ui.open_container`), forms and custom screens throw until they're built.
 8. **Mod channels** and keybinds.
 9. **Worldgen mods.** Worldgen URLs and mod ores go into the chunk worker `init` message. Workers must finish importing
    before generating anything. _Done for features and ores._ `register_terrain` throws until phase 3 moves the base
diff --git a/common/inventory.ts b/common/inventory.ts
index bb66e39..347fb25 100644
--- a/common/inventory.ts
+++ b/common/inventory.ts
@@ -49,7 +49,7 @@ export class ContainerSlot {
 	#item_stack: ItemStack | undefined;
 
 	has_item() {
-		return this.#item_stack !== undefined;
+		return this.get_item() !== undefined;
 	}
 
 	set_item(item_stack: ItemStack | undefined) {
@@ -60,11 +60,15 @@ export class ContainerSlot {
 	}
 
 	get_item() {
+		// scripts can count a stack down to nothing, it's gone then
+		if (this.#item_stack && this.#item_stack.amount <= 0) {
+			this.#item_stack = undefined;
+		}
 		return this.#item_stack;
 	}
 
 	get type_id() {
-		return this.#item_stack?.type_id;
+		return this.get_item()?.type_id;
 	}
 
 	set amount(new_amount: number) {
@@ -77,11 +81,11 @@ export class ContainerSlot {
 	}
 
 	get amount(): number | undefined {
-		return this.#item_stack?.amount;
+		return this.get_item()?.amount;
 	}
 
 	get max_amount() {
-		return this.#item_stack?.max_amount;
+		return this.get_item()?.max_amount;
 	}
 }
 
diff --git a/common/mod_api/server.ts b/common/mod_api/server.ts
index 88af2f6..870beb4 100644
--- a/common/mod_api/server.ts
+++ b/common/mod_api/server.ts
@@ -12,6 +12,7 @@ export interface ServerContext {
 	world: ServerWorld;
 	players: PlayerList;
 	containers: ContainerApi;
+	items: ItemApi;
 	recipes: RecipeApi;
 	ui: ServerUi;
 	net: ServerNet;
@@ -123,6 +124,8 @@ export interface ServerWorld {
 	get_state(x: number, y: number, z: number, name: string): number | undefined;
 	set_state(x: number, y: number, z: number, name: string, value: number): boolean;
 	get_block_data<T>(x: number, y: number, z: number): T | undefined;
+	// pops an item out of the block at x y z, like a broken block's drops
+	drop_item(x: number, y: number, z: number, item: ItemStack): void;
 	is_loaded(x: number, z: number): boolean;
 	readonly seed: string;
 }
@@ -177,6 +180,12 @@ export interface ContainerApi {
 	delete(id: string): void;
 }
 
+export interface ItemApi {
+	exists(id: Id): boolean;
+	// how many fit in one slot
+	max_stack(id: Id): number;
+}
+
 export interface RecipeApi {
 	furnace_result(input: Id): { output: ItemStack; cook_time: number } | undefined;
 	fuel_value(item: Id): number; // burn time in ticks, 0 if it isn't fuel
@@ -214,20 +223,39 @@ export type FormResult<T> = ({ canceled: true } & Partial<T>) | ({ canceled: fal
 export type SlotFilter = "smeltable" | "fuel" | ((item: ItemStack) => boolean);
 
 export interface ContainerScreenOptions {
-	title: string;
 	container: Container;
-	// x and y in slot units
-	layout: { slot: number; x: number; y: number; filter?: SlotFilter; output_only?: boolean }[];
-	player_inventory?: boolean;
-	bars?: { id: string; x: number; y: number; texture: Id }[];
-	labels?: { x: number; y: number; property: string }[];
+	// x and y in slot units, below the player's inventory. can be fractional
+	layout: {
+		slot: number;
+		x: number;
+		y: number;
+		// what can be put in, checked on the server
+		filter?: SlotFilter;
+		// can only be taken from, all at once, like the furnace result
+		output_only?: boolean;
+	}[];
+	// height of the screen's area in slots, fits the layout and bars when not set
+	rows?: number;
+	// progress bars, filled with the property value divided by the property max
+	bars?: {
+		x: number;
+		y: number;
+		value: string;
+		max: string;
+		direction: "up" | "right";
+		empty_texture: Id;
+		full_texture: Id;
+	}[];
 }
 
 export interface ScreenHandle<Props = unknown> {
 	readonly player: Player;
+	readonly open: boolean;
+	// numbers the bars show, synced to the player when they change
 	set_property(id: string, value: number): void;
 	update(props: Props): void; // custom screens only
 	close(): void;
+	// when it closes for any reason: the player closed it, left, opened another screen, or it was closed
 	on_close(fn: () => void): void;
 }
 
diff --git a/mods/bworld/blocks/chest.json b/mods/bworld/blocks/chest.json
index b1cd08b..2fefe62 100644
--- a/mods/bworld/blocks/chest.json
+++ b/mods/bworld/blocks/chest.json
@@ -8,6 +8,11 @@
 			"tool": "axe"
 		},
 		"drops": "bworld:chest",
-		"interactive": true
+		"interactive": true,
+		"components": {
+			"bworld:storage": {
+				"rows": 3
+			}
+		}
 	}
 }
diff --git a/mods/bworld/blocks/dirt.json b/mods/bworld/blocks/dirt.json
index 3945190..af17b2c 100644
--- a/mods/bworld/blocks/dirt.json
+++ b/mods/bworld/blocks/dirt.json
@@ -7,6 +7,12 @@
 			"toughness": 2,
 			"tool": "shovel"
 		},
-		"drops": "bworld:dirt"
+		"drops": "bworld:dirt",
+		"components": {
+			"bworld:hoeable": {
+				"tool": "bworld:hoe",
+				"into": "bworld:hoed_dirt"
+			}
+		}
 	}
 }
diff --git a/mods/bworld/blocks/furnace.json b/mods/bworld/blocks/furnace.json
index 19f670c..08b56c7 100644
--- a/mods/bworld/blocks/furnace.json
+++ b/mods/bworld/blocks/furnace.json
@@ -12,6 +12,9 @@
 			"requires_tool": true
 		},
 		"drops": "bworld:furnace",
-		"interactive": true
+		"interactive": true,
+		"components": {
+			"bworld:furnace": {}
+		}
 	}
 }
diff --git a/mods/bworld/blocks/grass.json b/mods/bworld/blocks/grass.json
index c9d458d..cc272bd 100644
--- a/mods/bworld/blocks/grass.json
+++ b/mods/bworld/blocks/grass.json
@@ -12,6 +12,12 @@
 			"tool": "shovel"
 		},
 		"drops": "bworld:dirt",
-		"item": false
+		"item": false,
+		"components": {
+			"bworld:hoeable": {
+				"tool": "bworld:hoe",
+				"into": "bworld:hoed_dirt"
+			}
+		}
 	}
 }
diff --git a/mods/bworld/blocks/wheat.json b/mods/bworld/blocks/wheat.json
index efc6524..baa6597 100644
--- a/mods/bworld/blocks/wheat.json
+++ b/mods/bworld/blocks/wheat.json
@@ -61,6 +61,12 @@
 				"bits": 3,
 				"default": 0
 			}
-		]
+		],
+		"components": {
+			"bworld:crop": {
+				"fertilizer": "bworld:bone_meal",
+				"max_age": 7
+			}
+		}
 	}
 }
diff --git a/mods/bworld/items/watering_can.json b/mods/bworld/items/watering_can.json
index c24815b..a90e526 100644
--- a/mods/bworld/items/watering_can.json
+++ b/mods/bworld/items/watering_can.json
@@ -2,6 +2,11 @@
 	"format_version": 1,
 	"item": {
 		"id": "bworld:watering_can",
-		"texture": "bworld:watering_can"
+		"texture": "bworld:watering_can",
+		"components": {
+			"bworld:watering_can": {
+				"max_water": 32
+			}
+		}
 	}
 }
diff --git a/mods/bworld/manifest.json b/mods/bworld/manifest.json
index 417809e..9a197e0 100644
--- a/mods/bworld/manifest.json
+++ b/mods/bworld/manifest.json
@@ -4,7 +4,12 @@
 	"name": "bworld",
 	"description": "The base game: its blocks, items, recipes and world.",
 	"version": "0.1.0",
-	"authors": ["paula"],
+	"authors": [
+		"paula"
+	],
 	"game_version": ">=0.1.0",
-	"credits": "CREDITS.md"
+	"credits": "CREDITS.md",
+	"scripts": {
+		"server": "scripts/server.ts"
+	}
 }
diff --git a/mods/bworld/scripts/server.ts b/mods/bworld/scripts/server.ts
new file mode 100644
index 0000000..58f56ec
--- /dev/null
+++ b/mods/bworld/scripts/server.ts
@@ -0,0 +1,234 @@
+// the base game's block and item behavior, written against the same api as any other mod
+import type { BlockRef, Container, ScreenHandle, ServerContext } from "bworld/server";
+
+export function setup(ctx: ServerContext) {
+	register_hoeable(ctx);
+	register_storage(ctx);
+	register_furnace(ctx);
+	register_crop(ctx);
+	register_watering_can(ctx);
+}
+
+// right clicking with a tool turns the block into another, like a hoe on grass
+function register_hoeable(ctx: ServerContext) {
+	ctx.components.register_block<{ tool: string; into: string }>("bworld:hoeable", {
+		on_interact(block, params, player) {
+			if (player.held_item?.id !== params.tool) {
+				return false;
+			}
+			ctx.world.set_block(block.x, block.y, block.z, params.into);
+			return true;
+		},
+	});
+}
+
+// the container a block keeps its items in, made the first time it's needed. blocks placed before tile data
+// existed don't have one yet
+function block_container(ctx: ServerContext, block: BlockRef, size: number): Container {
+	const existing = block.data?.container && ctx.containers.get(block.data.container);
+	if (existing) {
+		return existing;
+	}
+	const container = ctx.containers.create(size);
+	block.data = { ...block.data, container: container.id };
+	return container;
+}
+
+// what was inside falls out, like minecraft's Containers.dropContents
+function drop_contents(ctx: ServerContext, block: BlockRef) {
+	const container = block.data?.container && ctx.containers.get(block.data.container);
+	if (!container) {
+		return;
+	}
+	for (let slot = 0; slot < container.size; slot++) {
+		const item = container.get(slot);
+		if (item) {
+			ctx.world.drop_item(block.x, block.y, block.z, item);
+		}
+	}
+	ctx.containers.delete(container.id);
+}
+
+// a chest
+function register_storage(ctx: ServerContext) {
+	ctx.components.register_block<{ rows: number }>("bworld:storage", {
+		on_create(block, params) {
+			block_container(ctx, block, params.rows * 9);
+		},
+		on_interact(block, params, player) {
+			const size = params.rows * 9;
+			ctx.ui.open_container(player, {
+				container: block_container(ctx, block, size),
+				layout: Array.from({ length: size }, (_, slot) => ({ slot, x: slot % 9, y: Math.floor(slot / 9) })),
+				rows: params.rows,
+			});
+			return true;
+		},
+		on_break(block) {
+			drop_contents(ctx, block);
+		},
+	});
+}
+
+// furnace
+
+// slot 0 is what's smelting, 1 the fuel, 2 the result
+interface FurnaceData {
+	container: string;
+	// ticks
+	progress: number;
+	progress_max: number;
+	fuel: number;
+	fuel_max: number;
+}
+
+const FURNACE_BARS = [
+	{
+		x: 3.5,
+		y: 1,
+		value: "fuel",
+		max: "fuel_max",
+		direction: "up" as const,
+		empty_texture: "bworld:fire_empty",
+		full_texture: "bworld:fire_full",
+	},
+	{
+		x: 4.5,
+		y: 1,
+		value: "progress",
+		max: "progress_max",
+		direction: "right" as const,
+		empty_texture: "bworld:arrow_empty",
+		full_texture: "bworld:arrow_full",
+	},
+];
+
+function register_furnace(ctx: ServerContext) {
+	// who's looking at each furnace, by position, to keep their bars moving
+	const viewers = new Map<string, Set<ScreenHandle>>();
+	const key = (block: BlockRef) => `${block.x},${block.y},${block.z}`;
+
+	const furnace_data = (block: BlockRef): FurnaceData => {
+		const container = block_container(ctx, block, 3);
+		block.data = { progress: 0, progress_max: 0, fuel: 0, fuel_max: 0, ...block.data, container: container.id };
+		return block.data;
+	};
+
+	const show = (screen: ScreenHandle, data: FurnaceData) => {
+		screen.set_property("progress", data.progress);
+		screen.set_property("progress_max", data.progress_max);
+		screen.set_property("fuel", data.fuel);
+		screen.set_property("fuel_max", data.fuel_max);
+	};
+
+	// there's somewhere for the result to go
+	const can_smelt = (container: Container, output: { id: string; count: number }) => {
+		const result = container.get(2);
+		return !result || (result.id === output.id && result.count < ctx.items.max_stack(result.id));
+	};
+
+	ctx.components.register_block("bworld:furnace", {
+		on_create(block) {
+			furnace_data(block);
+		},
+		on_interact(block, _params, player) {
+			const data = furnace_data(block);
+			const screen = ctx.ui.open_container(player, {
+				container: ctx.containers.get(data.container)!,
+				layout: [
+					{ slot: 0, x: 3.5, y: 0 },
+					{ slot: 1, x: 3.5, y: 2, filter: "fuel" },
+					{ slot: 2, x: 5.5, y: 1, output_only: true },
+				],
+				rows: 3,
+				bars: FURNACE_BARS,
+			});
+			show(screen, data);
+			const screens = viewers.get(key(block)) ?? new Set();
+			viewers.set(key(block), screens);
+			screens.add(screen);
+			screen.on_close(() => screens.delete(screen));
+			return true;
+		},
+		on_break(block) {
+			drop_contents(ctx, block);
+		},
+		on_tick(block) {
+			const data = furnace_data(block);
+			const container = ctx.containers.get(data.container)!;
+			const input = container.get(0);
+			const recipe = input && ctx.recipes.furnace_result(input.id);
+
+			if (data.fuel > 0) {
+				data.fuel -= 1;
+			}
+
+			if (!recipe || !can_smelt(container, recipe.output)) {
+				data.progress = 0;
+			} else {
+				// refuel
+				const fuel = container.get(1);
+				if (data.fuel === 0 && fuel && ctx.recipes.is_fuel(fuel.id)) {
+					data.fuel = ctx.recipes.fuel_value(fuel.id);
+					data.fuel_max = data.fuel;
+					fuel.count -= 1;
+				}
+
+				// cook
+				if (data.fuel > 0) {
+					data.progress_max = recipe.cook_time;
+					data.progress += 1;
+					if (data.progress >= recipe.cook_time) {
+						data.progress = 0;
+						const result = container.get(2);
+						if (result) {
+							result.count += recipe.output.count;
+						} else {
+							container.set(2, recipe.output);
+						}
+						input.count -= 1;
+					}
+				}
+			}
+
+			for (const screen of viewers.get(key(block)) ?? []) show(screen, data);
+		},
+	});
+}
+
+// grows one stage each time it's right clicked with the fertilizer, like bone meal on wheat
+function register_crop(ctx: ServerContext) {
+	ctx.components.register_block<{ fertilizer: string; max_age: number }>("bworld:crop", {
+		on_interact(block, params, player) {
+			const held = player.held_item;
+			if (held?.id !== params.fertilizer) {
+				return false;
+			}
+			const age = ctx.world.get_state(block.x, block.y, block.z, "age") ?? 0;
+			// fully grown, keep the fertilizer
+			if (age >= params.max_age) {
+				return false;
+			}
+			ctx.world.set_state(block.x, block.y, block.z, "age", age + 1);
+			held.count -= 1;
+			return true;
+		},
+	});
+}
+
+interface WateringCanData {
+	water: number;
+	max_water: number;
+}
+
+function register_watering_can(ctx: ServerContext) {
+	ctx.components.register_item<{ max_water: number }>("bworld:watering_can", {
+		on_create(item, params) {
+			item.data = { water: 0, max_water: params.max_water } satisfies WateringCanData;
+		},
+		get_lore(item) {
+			const data = item.data as WateringCanData;
+			return `Water: ${data.water}/${data.max_water}`;
+		},
+	});
+}
diff --git a/server/game/blocks.ts b/server/game/blocks.ts
deleted file mode 100644
index a2b7ca0..0000000
--- a/server/game/blocks.ts
+++ /dev/null
@@ -1,287 +0,0 @@
-import { Container, ItemStack } from "$/common/inventory.ts";
-import { ScreenLayout } from "$/common/protocol.ts";
-import { BlockRegistry, EverythingRegistry, ItemRegistry } from "$/common/everything_registry.ts";
-import { get_state_value, set_state_value } from "$/common/utils.ts";
-import type { RecipeBook } from "$/common/mod_loader.ts";
-import type { GameServer } from "./game_server.ts";
-import type { ServerPlayer } from "./player.ts";
-import type { Tile } from "./world.ts";
-
-// what blocks do, only on the server. blocks without an entry just sit there
-export interface BlockBehavior {
-	// set up a tile for this block. blocks with this get a tile when placed
-	create_tile?(tile: Tile): void;
-	// right click, return true if it did something so no block gets placed
-	on_interact?(
-		game: GameServer,
-		block: { x: number; y: number; z: number; id: string },
-		player: ServerPlayer,
-	): boolean;
-	on_break?(game: GameServer, tile: Tile, player: ServerPlayer | undefined): void;
-	on_tick?(game: GameServer, tile: Tile): void;
-	on_second?(game: GameServer, tile: Tile): void;
-}
-
-export const BLOCK_BEHAVIORS: Record<string, BlockBehavior> = {};
-
-// whatever was inside falls out, like minecraft's Containers.dropContents
-function drop_container_contents(game: GameServer, tile: Tile) {
-	for (const container of Object.values(tile.containers)) {
-		for (let i = 0; i < container.size; i++) {
-			const item = container.get_item(i);
-			if (item) {
-				container.set_item(i, undefined);
-				game.pop_item(tile.x, tile.y, tile.z, item);
-			}
-		}
-	}
-}
-
-function hoe_into_hoed_dirt(
-	game: GameServer,
-	block: { x: number; y: number; z: number },
-	player: ServerPlayer,
-): boolean {
-	if (player.held_item?.type_id !== "bworld:hoe") {
-		return false;
-	}
-	game.set_block(block.x, block.y, block.z, "bworld:hoed_dirt", player);
-	return true;
-}
-
-BLOCK_BEHAVIORS["bworld:grass"] = { on_interact: hoe_into_hoed_dirt };
-BLOCK_BEHAVIORS["bworld:dirt"] = { on_interact: hoe_into_hoed_dirt };
-
-// crops
-
-// minecraft's bone meal: a crop grows 2 to 5 stages at once, and the bone meal is used up
-function grow_with_bone_meal(
-	game: GameServer,
-	block: { x: number; y: number; z: number; id: string },
-	player: ServerPlayer,
-): boolean {
-	const held = player.held_item;
-	if (held?.type_id !== "bworld:bone_meal") {
-		return false;
-	}
-	const info = EverythingRegistry.get<BlockRegistry>("blocks", block.id)!;
-	const value = game.world.get_block_value(block.x, block.y, block.z);
-	const age = get_state_value(value, info, "age")!;
-	const max_age = 2 ** info.states!.find((s) => s.name === "age")!.bits - 1;
-	// fully grown, keep the bone meal
-	if (age >= max_age) {
-		return false;
-	}
-
-	const new_age = Math.min(age + 1, max_age);
-	game.set_block_state(block.x, block.y, block.z, set_state_value(value, info, "age", new_age)! >>> 16);
-	const slot = player.inventory.get_slot(player.selected_slot);
-	slot.amount = slot.amount! - 1;
-	return true;
-}
-
-BLOCK_BEHAVIORS["bworld:wheat"] = { on_interact: grow_with_bone_meal };
-
-// chest
-
-const CHEST_LAYOUT: ScreenLayout = {
-	rows: 3,
-	slots: Array.from({ length: 9 * 3 }, (_, index) => ({ index, x: index % 9, y: Math.floor(index / 9) })),
-	bars: [],
-};
-
-BLOCK_BEHAVIORS["bworld:chest"] = {
-	create_tile(tile) {
-		tile.containers.main = new Container(9 * 3);
-	},
-	on_interact(game, block, player) {
-		const tile = game.get_or_create_tile(block.x, block.y, block.z);
-		game.open_screen(player, {
-			tile,
-			container: tile.containers.main,
-			layout: CHEST_LAYOUT,
-			properties: () => ({}),
-		});
-		return true;
-	},
-	on_break(game, tile) {
-		drop_container_contents(game, tile);
-	},
-};
-
-// furnace
-
-interface FurnaceData {
-	progress: number;
-	progress_max: number;
-	fuel: number;
-	fuel_max: number;
-}
-
-interface FurnaceRecipe {
-	output: { id: string; count: number };
-	cook_time: number;
-}
-
-function get_recipe(recipes: RecipeBook, input?: ItemStack | undefined): FurnaceRecipe | undefined {
-	if (!input) {
-		return;
-	}
-
-	return recipes.furnace.get(input.type_id);
-}
-
-function can_craft(container: Container, recipe?: FurnaceRecipe) {
-	if (!recipe) {
-		return false;
-	}
-
-	const output = container.get_item(2);
-
-	if (!output) {
-		return true;
-	}
-
-	if (output.type_id !== recipe.output.id) {
-		return false;
-	}
-
-	return output.amount < output.max_amount;
-}
-
-function get_fuel_value(recipes: RecipeBook, item?: ItemStack | undefined): number {
-	if (!item) {
-		return 0;
-	}
-	return recipes.fuel.get(item.type_id) ?? 0;
-}
-
-function has_fuel(recipes: RecipeBook, container: Container) {
-	return get_fuel_value(recipes, container.get_item(1)) > 0;
-}
-
-function consume_fuel(recipes: RecipeBook, container: Container): number {
-	const fuel = container.get_slot(1)!;
-	const value = get_fuel_value(recipes, fuel.get_item());
-
-	if (fuel.has_item()) {
-		fuel.amount! -= 1;
-	}
-
-	return value;
-}
-
-function craft(container: Container, recipe: FurnaceRecipe) {
-	const input = container.get_item(0)!;
-	const output = container.get_item(2);
-
-	if (!output) {
-		container.set_item(2, new ItemStack(recipe.output.id, recipe.output.count));
-	} else {
-		output.amount += recipe.output.count;
-	}
-
-	input.amount -= 1;
-	container.set_item(0, input.amount > 0 ? input : undefined);
-}
-
-const FURNACE_LAYOUT: ScreenLayout = {
-	rows: 3,
-	slots: [
-		{ index: 0, x: 3.5, y: 0 },
-		{ index: 1, x: 3.5, y: 2 },
-		{ index: 2, x: 5.5, y: 1, output: true },
-	],
-	bars: [
-		{
-			x: 3.5,
-			y: 1,
-			value: "fuel",
-			max: "fuel_max",
-			direction: "up",
-			empty_texture: "bworld:fire_empty",
-			full_texture: "bworld:fire_full",
-		},
-		{
-			x: 4.5,
-			y: 1,
-			value: "progress",
-			max: "progress_max",
-			direction: "right",
-			empty_texture: "bworld:arrow_empty",
-			full_texture: "bworld:arrow_full",
-		},
-	],
-};
-
-BLOCK_BEHAVIORS["bworld:furnace"] = {
-	create_tile(tile) {
-		tile.containers.main = new Container(3);
-		tile.data = { progress: 0, progress_max: 0, fuel: 0, fuel_max: 0 } satisfies FurnaceData;
-	},
-	on_interact(game, block, player) {
-		const tile = game.get_or_create_tile(block.x, block.y, block.z);
-		const data = tile.data as unknown as FurnaceData;
-		game.open_screen(player, {
-			tile,
-			container: tile.containers.main,
-			layout: FURNACE_LAYOUT,
-			properties: () => ({ ...data }),
-		});
-		return true;
-	},
-	on_break(game, tile) {
-		drop_container_contents(game, tile);
-	},
-	on_tick(game, tile) {
-		const data = tile.data as unknown as FurnaceData;
-		const container = tile.containers.main;
-
-		const input = container.get_item(0);
-		const recipe = get_recipe(game.recipes, input);
-
-		// burn fuel
-		if (data.fuel > 0) {
-			data.fuel -= 1;
-		}
-
-		if (!can_craft(container, recipe)) {
-			data.progress = 0;
-			return;
-		}
-
-		// refuel
-		if (data.fuel === 0 && has_fuel(game.recipes, container)) {
-			data.fuel = consume_fuel(game.recipes, container);
-			data.fuel_max = data.fuel;
-		}
-
-		// cook
-		if (data.fuel > 0 && recipe) {
-			data.progress_max = recipe.cook_time;
-			data.progress += 1;
-
-			if (data.progress >= recipe.cook_time) {
-				data.progress = 0;
-				craft(container, recipe);
-			}
-		}
-	},
-};
-
-// items that still need code, until they're components in mods/bworld (phase 2 in MODS.md)
-
-export interface WateringCanData {
-	water: number;
-	max_water: number;
-}
-
-export function add_base_item_hooks() {
-	const watering_can = EverythingRegistry.get<ItemRegistry<WateringCanData>>("items", "bworld:watering_can");
-	if (watering_can) {
-		watering_can.on_create = (item) => {
-			item.data = { water: 0, max_water: 32 };
-		};
-		watering_can.get_lore = (item) => `Water: ${item.data?.water}/${item.data?.max_water}`;
-	}
-}
diff --git a/server/game/game_server.ts b/server/game/game_server.ts
index 0eeec7d..df3fef9 100644
--- a/server/game/game_server.ts
+++ b/server/game/game_server.ts
@@ -26,7 +26,6 @@ import {
 } from "$/common/protocol.ts";
 import type { AtlasListing, ModListing, RecipeBook } from "$/common/mod_loader.ts";
 import type { WorldgenSetup } from "$/common/generation.ts";
-import { BLOCK_BEHAVIORS } from "./blocks.ts";
 import { ModRuntime, run_guarded } from "./mod_runtime.ts";
 import type { GameLoop } from "./game_loop.ts";
 import { consume_recipe_items, update_crafting_result } from "./crafting.ts";
@@ -61,19 +60,12 @@ export interface GameHost {
 }
 
 export interface SavedWorld {
-	version: 2;
+	version: 3;
 	seed: string;
 	changes: BlockChange[];
-	tiles: {
-		id: string;
-		x: number;
-		y: number;
-		z: number;
-		data: Record<string, unknown>;
-		containers: Record<string, (ItemData | null)[]>;
-		// a mod block's data, what BlockRef.data holds
-		mod_data?: unknown;
-	}[];
+	tiles: SavedTile[];
+	// every ctx.containers container, by id
+	containers?: Record<string, (ItemData | null)[]>;
 	players: Record<string, SavedPlayer>;
 	// items on the ground
 	entities?: SavedItemEntity[];
@@ -81,6 +73,18 @@ export interface SavedWorld {
 	mod_storage?: Record<string, Record<string, unknown>>;
 }
 
+interface SavedTile {
+	id: string;
+	x: number;
+	y: number;
+	z: number;
+	// what BlockRef.data holds
+	mod_data?: unknown;
+	// version 2, when chests and furnaces were engine code: their fields and their items
+	data?: Record<string, unknown>;
+	containers?: Record<string, (ItemData | null)[]>;
+}
+
 // the loaded mods, see load_mods.ts
 export interface GameMods {
 	listings: ModListing[];
@@ -102,6 +106,8 @@ export class GameServer {
 	#entities = new Map<string, ItemEntity>();
 	#next_entity_id = 1;
 	#mods: GameMods;
+	// ctx.containers, saved with the world
+	containers = new Map<string, Container>();
 	mods: ModRuntime;
 	recipes: RecipeBook;
 	// what runs tick(), for /tps. tests call tick() themselves
@@ -118,20 +124,20 @@ export class GameServer {
 		this.world = new ServerWorld(saved?.seed ?? default_seed, mods.worldgen);
 		this.mods.storage = saved?.mod_storage ?? {};
 		this.world.load_changes(saved?.changes ?? []);
+		for (const [id, items] of Object.entries(saved?.containers ?? {})) {
+			const container = new Container(items.length);
+			container.load(items);
+			this.containers.set(id, container);
+		}
 		for (const tile of saved?.tiles ?? []) {
-			const containers: Record<string, Container> = {};
-			for (const [name, items] of Object.entries(tile.containers)) {
-				containers[name] = new Container(items.length);
-				containers[name].load(items);
-			}
-			this.world.tiles.set(`${tile.x},${tile.y},${tile.z}`, { ...tile, containers });
+			this.world.add_tile({ id: tile.id, x: tile.x, y: tile.y, z: tile.z, mod_data: this.#upgrade_tile(tile) });
 		}
 		for (const entity of saved?.entities ?? []) {
 			const item = ItemEntity.load(this.#new_entity_id(), entity);
 			this.#entities.set(item.id, item);
 		}
 		this.#saved_players = saved?.players ?? {};
-		this.world.dirty = saved?.version !== 2;
+		this.world.dirty = saved?.version !== 3;
 
 		this.world.on_block_change = (x, y, z, id, state) =>
 			this.#broadcast(state ? { type: "set_block", x, y, z, id, state } : { type: "set_block", x, y, z, id });
@@ -185,28 +191,21 @@ export class GameServer {
 		const second = this.#tick % TICKS_PER_SECOND === 0;
 
 		for (const tile of [...this.world.tiles.values()]) {
-			const behavior = BLOCK_BEHAVIORS[tile.id];
+			if (tile.mod_data === undefined) {
+				continue;
+			}
 			const components = this.mods.components_of(tile.id)
 				.filter(({ component }) => component.on_tick || component.on_second);
-			if (!behavior?.on_tick && !behavior?.on_second && components.length === 0) {
+			if (components.length === 0 || !this.#near_any_player(tile.x, tile.z)) {
 				continue;
 			}
-			if (!this.#near_any_player(tile.x, tile.z)) {
-				continue;
-			}
-			behavior?.on_tick?.(this, tile);
-			if (second) {
-				behavior?.on_second?.(this, tile);
-			}
-			if (components.length > 0 && tile.mod_data !== undefined) {
-				const block = this.mods.block_ref(tile.x, tile.y, tile.z, tile.id);
-				for (const { mod, id, component, params } of components) {
-					if (component.on_tick) {
-						run_guarded(mod, `${id} on_tick`, () => component.on_tick!(block, params, TICK_DELTA));
-					}
-					if (second && component.on_second) {
-						run_guarded(mod, `${id} on_second`, () => component.on_second!(block, params, 1));
-					}
+			const block = this.mods.block_ref(tile.x, tile.y, tile.z, tile.id);
+			for (const { mod, id, component, params } of components) {
+				if (component.on_tick) {
+					run_guarded(mod, `${id} on_tick`, () => component.on_tick!(block, params, TICK_DELTA));
+				}
+				if (second && component.on_second) {
+					run_guarded(mod, `${id} on_second`, () => component.on_second!(block, params, 1));
 				}
 			}
 			// tile data can change on any tick, saving is cheap enough to not track it exactly
@@ -235,7 +234,7 @@ export class GameServer {
 			this.#saved_players[player.name] = player.save();
 		}
 		const saved: SavedWorld = {
-			version: 2,
+			version: 3,
 			seed: this.world.seed,
 			changes: this.world.all_changes(),
 			tiles: [...this.world.tiles.values()].map((tile) => ({
@@ -243,12 +242,11 @@ export class GameServer {
 				x: tile.x,
 				y: tile.y,
 				z: tile.z,
-				data: tile.data,
-				containers: Object.fromEntries(
-					Object.entries(tile.containers).map(([name, container]) => [name, container.to_data()]),
-				),
 				mod_data: tile.mod_data,
 			})),
+			containers: Object.fromEntries(
+				[...this.containers].map(([id, container]) => [id, container.to_data()]),
+			),
 			players: this.#saved_players,
 			entities: [...this.#entities.values()].map((entity) => entity.save()),
 			mod_storage: this.mods.storage,
@@ -365,24 +363,9 @@ export class GameServer {
 			}
 		}
 
-		const old_tile = this.world.get_tile(x, y, z);
-		if (old_tile) {
-			BLOCK_BEHAVIORS[old_tile.id]?.on_break?.(this, old_tile, player);
-			this.world.remove_tile(x, y, z);
-			for (const other of this.#players.values()) {
-				if (other.screen?.tile === old_tile) {
-					this.#close_screen(other);
-					this.#send(other, { type: "close_screen" });
-				}
-			}
-		}
-
+		this.world.remove_tile(x, y, z);
 		this.world.set_block(x, y, z, id, state);
 
-		if (BLOCK_BEHAVIORS[id]?.create_tile) {
-			this.get_or_create_tile(x, y, z);
-		}
-
 		if (id !== AIR_ID) {
 			const block = this.mods.block_ref(x, y, z, id);
 			for (const { mod, id: component_id, component, params } of this.mods.components_of(id)) {
@@ -396,23 +379,72 @@ export class GameServer {
 	get_or_create_tile(x: number, y: number, z: number): Tile {
 		let tile = this.world.get_tile(x, y, z);
 		if (!tile) {
-			// blocks placed before tiles were saved have none yet
-			const id = this.world.get_block_id(x, y, z);
-			tile = { id, x, y, z, data: {}, containers: {} };
-			BLOCK_BEHAVIORS[id]?.create_tile?.(tile);
+			tile = { id: this.world.get_block_id(x, y, z), x, y, z };
 			this.world.add_tile(tile);
 		}
 		return tile;
 	}
 
+	// containers
+
+	create_container(size: number): { id: string; container: Container } {
+		const id = crypto.randomUUID();
+		const container = new Container(size);
+		this.containers.set(id, container);
+		this.world.dirty = true;
+		return { id, container };
+	}
+
+	// anyone looking at it gets their screen closed
+	delete_container(id: string) {
+		const container = this.containers.get(id);
+		if (!container) {
+			return;
+		}
+		this.containers.delete(id);
+		this.world.dirty = true;
+		for (const player of this.#players.values()) {
+			if (player.screen?.container === container) {
+				this.close_screen(player);
+			}
+		}
+	}
+
+	// screens
+
 	open_screen(player: ServerPlayer, screen: OpenScreen) {
 		this.#close_screen(player);
 		player.screen = screen;
-		this.#send(player, { type: "open_screen", layout: screen.layout, properties: screen.properties() });
-		player.sent.set("properties", JSON.stringify(screen.properties()));
+		this.#send(player, { type: "open_screen", layout: screen.layout, properties: { ...screen.properties } });
+		player.sent.set("properties", JSON.stringify(screen.properties));
 		player.sent.delete("screen");
 	}
 
+	// closes it for the player too, not just on the server
+	close_screen(player: ServerPlayer) {
+		if (!player.screen) {
+			return;
+		}
+		this.#close_screen(player);
+		this.#send(player, { type: "close_screen" });
+	}
+
+	// version 2 saves had chests and furnaces in the engine, with their fields in data and their items in
+	// containers.main. the components keep those fields and put the items in a ctx.containers container
+	#upgrade_tile(tile: SavedTile): unknown {
+		if (tile.mod_data !== undefined || (!tile.data && !tile.containers)) {
+			return tile.mod_data;
+		}
+		const data: Record<string, unknown> = { ...tile.data };
+		const items = tile.containers?.main;
+		if (items) {
+			const { id, container } = this.create_container(items.length);
+			container.load(items);
+			data.container = id;
+		}
+		return data;
+	}
+
 	// messages
 
 	// hello -> welcome, then ready -> join. see "Delivery to clients" in MODS.md
@@ -623,7 +655,7 @@ export class GameServer {
 			return;
 		}
 
-		let handled = BLOCK_BEHAVIORS[info.id]?.on_interact?.(this, { x, y, z, id: info.id }, player) ?? false;
+		let handled = false;
 		for (const { mod, id: component_id, component, params } of this.mods.components_of(info.id)) {
 			if (component.on_interact) {
 				handled = run_guarded(mod, `${component_id} on_interact`, () =>
@@ -715,6 +747,11 @@ export class GameServer {
 			if (item && take_output(item, player.cursor)) {
 				container.set_item(index, undefined);
 			}
+		} else if (
+			key === "screen" && player.cursor.item && !(player.screen?.filters.get(index)?.(player.cursor.item) ?? true)
+		) {
+			// the slot doesn't take what the cursor holds
+			return;
 		} else {
 			click_slot(container, index, player.cursor, button);
 		}
@@ -722,6 +759,9 @@ export class GameServer {
 		if (key === "crafting") {
 			update_crafting_result(container, this.recipes.shaped);
 		}
+		if (key === "screen") {
+			this.world.dirty = true;
+		}
 	}
 
 	#chat(player: ServerPlayer, raw: unknown) {
@@ -756,8 +796,16 @@ export class GameServer {
 				this.#send(player, { type: "chat", text: "Usage: /give <item> [count]" });
 				return;
 			}
+			// a name without a namespace works when only one mod has an item called that
 			if (!item_id.includes(":")) {
-				item_id = `bworld:${item_id}`;
+				const matches = EverythingRegistry.entries("items").map(([id]) => id).filter((id) =>
+					id.endsWith(`:${item_id}`)
+				);
+				if (matches.length > 1) {
+					this.#send(player, { type: "chat", text: `Which one? ${matches.join(", ")}` });
+					return;
+				}
+				item_id = matches[0] ?? item_id;
 			}
 			const amount = count === undefined ? 1 : Number(count);
 			if (!EverythingRegistry.get("items", item_id)) {
@@ -793,7 +841,9 @@ export class GameServer {
 	}
 
 	#close_screen(player: ServerPlayer) {
+		const screen = player.screen;
 		player.screen = undefined;
+		for (const fn of screen?.on_close ?? []) fn();
 		player.sent.delete("screen");
 		player.sent.delete("properties");
 
@@ -949,7 +999,7 @@ export class GameServer {
 		if (player.screen) {
 			const items = player.screen.container.to_data();
 			sync("screen", items, () => ({ type: "container", container: "screen", items }));
-			const properties = player.screen.properties();
+			const properties = { ...player.screen.properties };
 			sync("properties", properties, () => ({ type: "screen_properties", properties }));
 		}
 	}
diff --git a/server/game/load_mods.ts b/server/game/load_mods.ts
index 9177a4d..af155b3 100644
--- a/server/game/load_mods.ts
+++ b/server/game/load_mods.ts
@@ -3,7 +3,6 @@
 import { register_mod_data } from "$/common/mod_loader.ts";
 import type { AtlasListing, ModData, ModListing } from "$/common/mod_loader.ts";
 import { load_worldgen } from "$/common/worldgen_loader.ts";
-import { add_base_item_hooks } from "./blocks.ts";
 import { GameHost, GameServer } from "./game_server.ts";
 import { ModRuntime } from "./mod_runtime.ts";
 
@@ -23,7 +22,6 @@ export async function start_game(
 	mods: ServerModSource[],
 ): Promise<GameServer> {
 	const recipes = register_mod_data(mods.map((mod) => ({ id: mod.listing.id, data: mod.data })));
-	add_base_item_hooks();
 
 	const worldgen_scripts = mods.flatMap((mod) =>
 		mod.worldgen_url ? [{ mod: mod.listing.id, url: mod.worldgen_url }] : []
diff --git a/server/game/mod_runtime.ts b/server/game/mod_runtime.ts
index 08c83f0..74b5545 100644
--- a/server/game/mod_runtime.ts
+++ b/server/game/mod_runtime.ts
@@ -8,10 +8,12 @@ import type {
 	BlockRef,
 	Command,
 	Container,
+	ContainerScreenOptions,
 	EventSignal,
 	ItemComponent,
 	ItemStack,
 	Player,
+	ScreenHandle,
 	ServerAfterEvents,
 	ServerBeforeEvents,
 	ServerContext,
@@ -19,7 +21,8 @@ import type {
 import { ModLoadError } from "$/common/mod_loader.ts";
 import { AIR_ID } from "$/common/protocol.ts";
 import type { GameServer } from "./game_server.ts";
-import type { ServerPlayer } from "./player.ts";
+import type { OpenScreen, ServerPlayer } from "./player.ts";
+import type { ScreenLayout } from "$/common/protocol.ts";
 
 // a list of handlers that can't break each other: one throwing is logged under its mod and the rest still run
 export class Signal<T> {
@@ -107,6 +110,8 @@ export class ModRuntime {
 	#next_timer = 1;
 	#setting_up = true;
 	#players = new WeakMap<ServerPlayer, Player>();
+	// the other way, for apis that take a player
+	#server_players = new WeakMap<Player, ServerPlayer>();
 	game!: GameServer;
 
 	// imports each server script and calls its setup, in load order
@@ -152,6 +157,19 @@ export class ModRuntime {
 					);
 				}
 			}
+			const lore = components.filter(([component_id]) =>
+				this.item_components.get(component_id)!.component.get_lore
+			);
+			if (lore.length > 0) {
+				item.get_lore = (stack) =>
+					lore.map(([component_id, params]) => {
+						const { mod, component } = this.item_components.get(component_id)!;
+						return run_guarded(mod, `${component_id} get_lore`, () =>
+							component.get_lore!(item_api(stack), params));
+					}).filter((line) =>
+						typeof line === "string"
+					).join("\n");
+			}
 			// items are created all over the engine, hook their creation once here
 			const previous = item.on_create;
 			item.on_create = (stack) => {
@@ -231,6 +249,7 @@ export class ModRuntime {
 		if (!api) {
 			api = player_api(this.game, player);
 			this.#players.set(player, api);
+			this.#server_players.set(api, player);
 		}
 		return api;
 	}
@@ -339,6 +358,7 @@ export class ModRuntime {
 					return true;
 				},
 				get_block_data: (x, y, z) => game().world.get_tile(x, y, z)?.mod_data as never,
+				drop_item: (x, y, z, item) => void game().pop_item(x, y, z, new_stack(item)),
 				is_loaded: () => true,
 				get seed() {
 					return game().world.seed;
@@ -355,6 +375,14 @@ export class ModRuntime {
 					return p && this.player(p);
 				},
 			},
+			items: {
+				exists: (id) => EverythingRegistry.get("items", id) !== undefined,
+				max_stack: (id) => {
+					const item = EverythingRegistry.get<ItemRegistry>("items", id);
+					if (!item) throw new Error(`unknown item ${id}`);
+					return item.max_stack ?? 64;
+				},
+			},
 			recipes: {
 				furnace_result: (input) => {
 					const recipe = game().recipes.furnace.get(input);
@@ -364,8 +392,27 @@ export class ModRuntime {
 				is_fuel: (item) => game().recipes.fuel.has(item),
 				is_smeltable: (item) => game().recipes.furnace.has(item),
 			},
-			containers: not_yet_object(mod, "containers", "step 7 in MODS.md"),
-			ui: not_yet_object(mod, "ui", "step 7 in MODS.md"),
+			containers: {
+				create: (size) => {
+					if (!Number.isInteger(size) || size < 1 || size > MAX_CONTAINER_SIZE) {
+						throw new Error(`a container has 1 to ${MAX_CONTAINER_SIZE} slots, not ${size}`);
+					}
+					const { id, container } = game().create_container(size);
+					return container_api(game(), id, container);
+				},
+				get: (id) => {
+					const container = game().containers.get(id);
+					return container && container_api(game(), id, container);
+				},
+				delete: (id) => game().delete_container(id),
+			},
+			ui: {
+				open_container: (player, options) => this.#open_container(mod, player, options),
+				message_form: not_yet(mod, "ui.message_form", "step 7 in MODS.md"),
+				action_form: not_yet(mod, "ui.action_form", "step 7 in MODS.md"),
+				modal_form: not_yet(mod, "ui.modal_form", "step 7 in MODS.md"),
+				open_screen: not_yet(mod, "ui.open_screen", "step 7 in MODS.md"),
+			},
 			net: not_yet_object(mod, "net", "step 8 in MODS.md"),
 			storage: {
 				get: (key) => structuredClone(this.storage[mod]?.[key]) as never,
@@ -383,6 +430,78 @@ export class ModRuntime {
 		return ctx;
 	}
 
+	#open_container(mod: string, player: Player, options: ContainerScreenOptions): ScreenHandle {
+		const game = this.game;
+		const server_player = this.#server_players.get(player);
+		if (!server_player || !game.players().includes(server_player)) {
+			throw new Error(`${player.name} isn't online`);
+		}
+		const container = game.containers.get(options.container.id);
+		if (!container) {
+			throw new Error("open_container needs a container from ctx.containers");
+		}
+
+		const filters = new Map<number, (item: EngineItemStack) => boolean>();
+		for (const { slot, filter } of options.layout) {
+			if (!Number.isInteger(slot) || slot < 0 || slot >= container.size) {
+				throw new Error(`slot ${slot} isn't in the container, it has ${container.size}`);
+			}
+			if (filter === "smeltable") {
+				filters.set(slot, (item) => game.recipes.furnace.has(item.type_id));
+			} else if (filter === "fuel") {
+				filters.set(slot, (item) => game.recipes.fuel.has(item.type_id));
+			} else if (typeof filter === "function") {
+				filters.set(slot, (item) => run_guarded(mod, "a slot filter", () => filter(item_api(item))) === true);
+			}
+		}
+
+		const bars = options.bars ?? [];
+		const bottom = Math.max(0, ...options.layout.map((s) => s.y + 1), ...bars.map((b) => b.y + 1));
+		const layout: ScreenLayout = {
+			rows: options.rows ?? Math.ceil(bottom),
+			slots: options.layout.map(({ slot, x, y, output_only }) =>
+				output_only ? { index: slot, x, y, output: true } : { index: slot, x, y }
+			),
+			bars: bars.map(({ x, y, value, max, direction, empty_texture, full_texture }) => ({
+				x,
+				y,
+				value,
+				max,
+				direction,
+				empty_texture,
+				full_texture,
+			})),
+		};
+
+		let open = true;
+		const screen: OpenScreen = { container, layout, properties: {}, filters, on_close: [() => open = false] };
+		game.open_screen(server_player, screen);
+
+		return {
+			player,
+			get open() {
+				return open;
+			},
+			set_property(id, value) {
+				if (typeof value !== "number" || !Number.isFinite(value)) {
+					throw new Error(`property ${id} must be a number, not ${value}`);
+				}
+				screen.properties[id] = value;
+			},
+			update: not_yet(mod, "update", "custom screens are step 7 in MODS.md"),
+			close() {
+				if (server_player.screen === screen) game.close_screen(server_player);
+			},
+			on_close(fn) {
+				if (!open) {
+					run_guarded(mod, "a screen on_close", fn);
+					return;
+				}
+				screen.on_close.push(() => run_guarded(mod, "a screen on_close", fn));
+			},
+		};
+	}
+
 	#add_timer(mod: string, fn: () => void, ticks: number, every?: number) {
 		const handle = this.#next_timer++;
 		this.#timers.set(handle, { mod, fn, at: this.game.current_tick + Math.max(0, ticks), every });
@@ -426,6 +545,8 @@ function not_yet_object<T>(mod: string, name: string, where: string): T {
 	}) as T;
 }
 
+const MAX_CONTAINER_SIZE = 256;
+
 // the engine's item stacks as mods see them: { id, count, data }
 export function item_api(stack: EngineItemStack): ItemStack {
 	return {
@@ -454,22 +575,32 @@ function new_stack(item: ItemStack): EngineItemStack {
 	return stack;
 }
 
-function player_api(game: GameServer, player: ServerPlayer): Player {
-	const inventory: Container = {
-		id: `player:${player.id}`,
-		size: player.inventory.size,
+// an engine container as mods see it
+function container_api(game: GameServer, id: string, container: EngineContainer): Container {
+	return {
+		id,
+		size: container.size,
 		get: (slot) => {
-			const stack = player.inventory.get_item(slot);
+			const stack = container.get_item(slot);
 			return stack && item_api(stack);
 		},
-		set: (slot, item) => player.inventory.set_item(slot, item ? new_stack(item) : undefined),
+		set: (slot, item) => {
+			if (!Number.isInteger(slot) || slot < 0 || slot >= container.size) {
+				throw new Error(`slot ${slot} isn't in the container, it has ${container.size}`);
+			}
+			container.set_item(slot, item ? new_stack(item) : undefined);
+		},
 		add: (item) => {
 			const stack = new_stack(item);
-			const left = player.inventory.add_item(stack);
+			const left = container.add_item(stack);
 			return left > 0 ? { id: item.id, count: left, data: stack.data } : undefined;
 		},
-		on_change: (fn) => game.mods.watch_container(running_mod || "unknown", player.inventory, fn),
+		on_change: (fn) => game.mods.watch_container(running_mod || "unknown", container, fn),
 	};
+}
+
+function player_api(game: GameServer, player: ServerPlayer): Player {
+	const inventory = container_api(game, `player:${player.id}`, player.inventory);
 
 	return {
 		get id() {
diff --git a/server/game/player.ts b/server/game/player.ts
index a636790..503e517 100644
--- a/server/game/player.ts
+++ b/server/game/player.ts
@@ -1,16 +1,18 @@
 import { Container, Cursor, ItemData, ItemStack } from "$/common/inventory.ts";
 import { PlayerInfo, ScreenLayout } from "$/common/protocol.ts";
-import { Tile } from "./world.ts";
 
 export const INVENTORY_SIZE = 9 * 4;
 export const CRAFTING_SIZE = 10;
 
-// a screen the server opened for this player, showing a tile's container
+// a container screen a mod opened for this player, see ctx.ui.open_container
 export interface OpenScreen {
-	tile: Tile;
 	container: Container;
 	layout: ScreenLayout;
-	properties(): Record<string, number>;
+	// what the bars show, synced when they change
+	properties: Record<string, number>;
+	// what can go into each slot, checked when the player clicks
+	filters: Map<number, (item: ItemStack) => boolean>;
+	on_close: (() => void)[];
 }
 
 // what's saved about a player between sessions, by name
diff --git a/server/game/world.ts b/server/game/world.ts
index e29a9ab..18b20d5 100644
--- a/server/game/world.ts
+++ b/server/game/world.ts
@@ -1,7 +1,6 @@
 import { AIR, CHUNK_AREA, CHUNK_HEIGHT, CHUNK_SIZE, ID_MASK } from "$/common/constants.ts";
 import { BlockRegistry, EverythingRegistry } from "$/common/everything_registry.ts";
 import { generate_raw_chunk, RawChunk, WorldgenSetup } from "$/common/generation.ts";
-import { Container } from "$/common/inventory.ts";
 import { AIR_ID, BlockChange } from "$/common/protocol.ts";
 import { block_value, chunk_key, default_block_value } from "$/common/utils.ts";
 import { LruMap } from "./lru.ts";
@@ -12,15 +11,13 @@ const CHUNK_CACHE_SIZE = 256;
 // how far from the middle of the world to look for dry land to spawn on, in chunks
 const SPAWN_SEARCH_CHUNKS = 32;
 
-// a block with state the server keeps, like a chest's items. never sent to clients as is
+// a block with data the server keeps, like where a chest's items are. never sent to clients
 export interface Tile {
 	id: string;
 	x: number;
 	y: number;
 	z: number;
-	data: Record<string, unknown>;
-	containers: Record<string, Container>;
-	// a mod block's data, what BlockRef.data holds
+	// what BlockRef.data holds
 	mod_data?: unknown;
 }
 
diff --git a/tests/base_game_test.ts b/tests/base_game_test.ts
new file mode 100644
index 0000000..269a071
--- /dev/null
+++ b/tests/base_game_test.ts
@@ -0,0 +1,197 @@
+// the base game's block and item behavior: hoeing, chests, furnaces, crops and the watering can
+import { assert, assertEquals } from "@std/assert";
+import { BlockRegistry, EverythingRegistry } from "$/common/everything_registry.ts";
+import { get_state_value } from "$/common/utils.ts";
+import { test_game } from "./helpers.ts";
+
+// deno-lint-ignore no-explicit-any
+type Msg = any;
+type Game = Awaited<ReturnType<typeof test_game>>;
+
+const last_container = (messages: Msg[], container: string) =>
+	messages.filter((m) => m.type === "container" && m.container === container).at(-1)?.items;
+
+// a player standing on a stone floor at y 99, high above the terrain, with the items given in their inventory
+async function setup(items: [string, number][] = []) {
+	const t = await test_game("mods");
+	t.join(1, "alice");
+	for (let x = -3; x <= 3; x++) {
+		for (let z = -3; z <= 3; z++) t.game.set_block(x, 99, z, "bworld:stone");
+	}
+	t.send(1, { type: "move", x: 0.5, y: 100, z: 0.5, yaw: 0, pitch: 0 });
+	for (const [id, count] of items) t.send(1, { type: "chat", text: `/give ${id} ${count}` });
+	return t;
+}
+
+// the inventory slot holding an item, from what the server sent last
+function slot_of(messages: Msg[], id: string) {
+	const slot = (last_container(messages, "inventory") ?? []).findIndex((i: Msg) => i?.id === id);
+	assert(slot >= 0, `no ${id} in the inventory`);
+	return slot;
+}
+
+// picks a whole inventory stack up and puts it into a slot of the open screen
+function move_to_screen(t: Game, from: number, to: number) {
+	t.send(1, { type: "click", container: "inventory", index: from, button: 0 });
+	t.send(1, { type: "click", container: "screen", index: to, button: 0 });
+}
+
+Deno.test("a hoe turns grass and dirt into hoed dirt, anything else places nothing", async () => {
+	const t = await setup([["bworld:hoe", 1]]);
+	t.game.set_block(1, 100, 0, "bworld:grass");
+	t.game.set_block(2, 100, 0, "bworld:dirt");
+	t.send(1, { type: "select_slot", slot: slot_of(t.take(1), "bworld:hoe") });
+
+	t.send(1, { type: "use_block", x: 1, y: 100, z: 0, face: "top" });
+	t.send(1, { type: "use_block", x: 2, y: 100, z: 0, face: "top" });
+	assertEquals(t.game.world.get_block_id(1, 100, 0), "bworld:hoed_dirt");
+	assertEquals(t.game.world.get_block_id(2, 100, 0), "bworld:hoed_dirt");
+
+	// hoed dirt stays hoed dirt, and the hand doesn't do it
+	t.send(1, { type: "use_block", x: 1, y: 100, z: 0, face: "top" });
+	assertEquals(t.game.world.get_block_id(1, 100, 0), "bworld:hoed_dirt");
+	t.game.set_block(1, 100, 1, "bworld:grass");
+	t.send(1, { type: "select_slot", slot: 8 });
+	t.send(1, { type: "use_block", x: 1, y: 100, z: 1, face: "top" });
+	assertEquals(t.game.world.get_block_id(1, 100, 1), "bworld:grass");
+});
+
+Deno.test("a chest keeps items, shows them to everyone, and drops them when broken", async () => {
+	const t = await setup([["bworld:chest", 1], ["bworld:coal", 10]]);
+	t.game.set_block(1, 100, 0, "bworld:chest");
+	const coal = slot_of(t.take(1), "bworld:coal");
+
+	t.send(1, { type: "use_block", x: 1, y: 100, z: 0, face: "top" });
+	const opened = t.take(1).find((m) => m.type === "open_screen");
+	assertEquals(opened.layout.rows, 3);
+	assertEquals(opened.layout.slots.length, 27);
+	// nothing got placed on top
+	assertEquals(t.game.world.get_block_id(1, 101, 0), "bworld:air");
+
+	move_to_screen(t, coal, 4);
+	assertEquals(last_container(t.take(1), "screen")[4], { id: "bworld:coal", count: 10 });
+	t.send(1, { type: "close_screen" });
+
+	// still there after opening it again, and after saving and loading
+	const loaded = await test_game("mods", t.game.save());
+	loaded.join(1, "alice");
+	loaded.send(1, { type: "move", x: 0.5, y: 100, z: 0.5, yaw: 0, pitch: 0 });
+	loaded.send(1, { type: "use_block", x: 1, y: 100, z: 0, face: "top" });
+	assertEquals(last_container(loaded.take(1), "screen")[4], { id: "bworld:coal", count: 10 });
+
+	// breaking it closes the screen and drops the chest and what was inside
+	loaded.send(1, { type: "break_block", x: 1, y: 100, z: 0 });
+	const messages = loaded.take(1);
+	assert(messages.some((m) => m.type === "close_screen"));
+	const dropped = loaded.game.item_entities().map((e) => e.item.to_data());
+	assertEquals(
+		dropped.sort((a, b) => a.id.localeCompare(b.id)),
+		[{ id: "bworld:chest", count: 1 }, { id: "bworld:coal", count: 10 }],
+	);
+});
+
+Deno.test("a furnace burns fuel to smelt, shows its progress, and only lets the result be taken", async () => {
+	const t = await setup([["bworld:iron_ore", 2], ["bworld:coal", 1]]);
+	t.game.set_block(1, 100, 0, "bworld:furnace");
+	const messages = t.take(1);
+	const ore = slot_of(messages, "bworld:iron_ore");
+	const coal = slot_of(messages, "bworld:coal");
+
+	t.send(1, { type: "use_block", x: 1, y: 100, z: 0, face: "top" });
+	const opened = t.take(1).find((m) => m.type === "open_screen");
+	assertEquals(opened.layout.slots.map((s: Msg) => s.index), [0, 1, 2]);
+	assertEquals(opened.layout.slots[2].output, true);
+	assertEquals(opened.layout.bars.map((b: Msg) => b.value), ["fuel", "progress"]);
+
+	move_to_screen(t, ore, 0);
+	move_to_screen(t, coal, 1);
+	t.take(1);
+
+	// iron takes 200 ticks
+	for (let i = 0; i < 100; i++) t.game.tick();
+	const halfway = t.take(1).filter((m) => m.type === "screen_properties").at(-1).properties;
+	assertEquals(halfway.progress_max, 200);
+	assert(halfway.progress >= 98 && halfway.progress <= 100, `progress ${halfway.progress}`);
+	assertEquals(halfway.fuel_max, 1000);
+
+	for (let i = 0; i < 110; i++) t.game.tick();
+	const screen = last_container(t.take(1), "screen");
+	assertEquals(screen[0], { id: "bworld:iron_ore", count: 1 });
+	assertEquals(screen[1], null, "the coal got used");
+	assertEquals(screen[2], { id: "bworld:iron_ingot", count: 1 });
+
+	// nothing can be put into the result slot, but the result can be taken
+	t.send(1, { type: "click", container: "screen", index: 0, button: 0 });
+	t.send(1, { type: "click", container: "screen", index: 2, button: 0 });
+	assertEquals(last_container(t.take(1), "screen")[2], { id: "bworld:iron_ingot", count: 1 });
+	t.send(1, { type: "click", container: "screen", index: 0, button: 0 });
+	t.send(1, { type: "click", container: "screen", index: 2, button: 0 });
+	const after = t.take(1);
+	assertEquals(last_container(after, "screen")[2], null);
+	assertEquals(after.filter((m) => m.type === "cursor").at(-1).item, { id: "bworld:iron_ingot", count: 1 });
+});
+
+Deno.test("bone meal grows wheat until it's fully grown", async () => {
+	const t = await setup([["bworld:bone_meal", 8]]);
+	t.game.set_block(1, 100, 0, "bworld:wheat");
+	const wheat = EverythingRegistry.get<BlockRegistry>("blocks", "bworld:wheat")!;
+	const age = () => get_state_value(t.game.world.get_block_value(1, 100, 0), wheat, "age")!;
+	assertEquals(age(), 0);
+	const slot = slot_of(t.take(1), "bworld:bone_meal");
+	t.send(1, { type: "select_slot", slot });
+
+	// one stage at a time, and once it's fully grown it stops using bone meal
+	t.send(1, { type: "use_block", x: 1, y: 100, z: 0, face: "top" });
+	assertEquals(age(), 1);
+	for (let i = 0; i < 7; i++) t.send(1, { type: "use_block", x: 1, y: 100, z: 0, face: "top" });
+	assertEquals(age(), 7);
+	assertEquals(last_container(t.take(1), "inventory")[slot]?.count, 1);
+	assertEquals(t.game.world.get_block_id(1, 101, 0), "bworld:air");
+});
+
+Deno.test("the last bone meal is used up", async () => {
+	const t = await setup([["bworld:bone_meal", 1]]);
+	t.game.set_block(1, 100, 0, "bworld:wheat");
+	const slot = slot_of(t.take(1), "bworld:bone_meal");
+	t.send(1, { type: "select_slot", slot });
+	t.send(1, { type: "use_block", x: 1, y: 100, z: 0, face: "top" });
+	assertEquals(last_container(t.take(1), "inventory")[slot], null);
+});
+
+Deno.test("a new watering can starts empty", async () => {
+	const t = await setup([["bworld:watering_can", 1]]);
+	const can = last_container(t.take(1), "inventory").find((i: Msg) => i?.id === "bworld:watering_can");
+	assertEquals(can.data, { water: 0, max_water: 32 });
+});
+
+Deno.test("chests and furnaces from a world saved before they were mod code keep their items and keep smelting", async () => {
+	const t = await test_game("mods", Deno.readTextFileSync("tests/fixtures/world_v2.json"), "fixture-seed");
+	t.join(1, "alice");
+
+	t.send(1, { type: "use_block", x: 1, y: 100, z: 0, face: "top" });
+	const chest = last_container(t.take(1), "screen");
+	assertEquals(chest.length, 27);
+	assertEquals(chest[4], { id: "bworld:coal", count: 6 });
+	t.send(1, { type: "close_screen" });
+
+	t.send(1, { type: "use_block", x: 2, y: 100, z: 0, face: "top" });
+	let messages = t.take(1);
+	assertEquals(last_container(messages, "screen"), [
+		{ id: "bworld:iron_ore", count: 2 },
+		{ id: "bworld:coal", count: 2 },
+		{ id: "bworld:iron_ingot", count: 1 },
+	]);
+	const properties = messages.filter((m) => m.type === "screen_properties").at(-1).properties;
+	assertEquals(properties, { progress: 50, progress_max: 200, fuel: 751, fuel_max: 1000 });
+
+	// 150 more ticks finish the second ingot
+	for (let i = 0; i < 150; i++) t.game.tick();
+	messages = t.take(1);
+	assertEquals(last_container(messages, "screen")[2], { id: "bworld:iron_ingot", count: 2 });
+
+	// saved in the new format, nothing lost
+	const saved = JSON.parse(t.game.save());
+	assertEquals(saved.version, 3);
+	assert(saved.tiles.every((tile: Msg) => tile.data === undefined && tile.containers === undefined));
+	assertEquals(Object.keys(saved.containers).length, 2);
+});
diff --git a/tests/fixtures/world_v2.json b/tests/fixtures/world_v2.json
new file mode 100644
index 0000000..1dc9fc7
--- /dev/null
+++ b/tests/fixtures/world_v2.json
@@ -0,0 +1,436 @@
+{
+	"version": 2,
+	"seed": "fixture-seed",
+	"changes": [
+		[
+			-3,
+			99,
+			-3,
+			"bworld:stone"
+		],
+		[
+			-3,
+			99,
+			-2,
+			"bworld:stone"
+		],
+		[
+			-3,
+			99,
+			-1,
+			"bworld:stone"
+		],
+		[
+			-2,
+			99,
+			-3,
+			"bworld:stone"
+		],
+		[
+			-2,
+			99,
+			-2,
+			"bworld:stone"
+		],
+		[
+			-2,
+			99,
+			-1,
+			"bworld:stone"
+		],
+		[
+			-1,
+			99,
+			-3,
+			"bworld:stone"
+		],
+		[
+			-1,
+			99,
+			-2,
+			"bworld:stone"
+		],
+		[
+			-1,
+			99,
+			-1,
+			"bworld:stone"
+		],
+		[
+			-3,
+			99,
+			0,
+			"bworld:stone"
+		],
+		[
+			-3,
+			99,
+			1,
+			"bworld:stone"
+		],
+		[
+			-3,
+			99,
+			2,
+			"bworld:stone"
+		],
+		[
+			-3,
+			99,
+			3,
+			"bworld:stone"
+		],
+		[
+			-2,
+			99,
+			0,
+			"bworld:stone"
+		],
+		[
+			-2,
+			99,
+			1,
+			"bworld:stone"
+		],
+		[
+			-2,
+			99,
+			2,
+			"bworld:stone"
+		],
+		[
+			-2,
+			99,
+			3,
+			"bworld:stone"
+		],
+		[
+			-1,
+			99,
+			0,
+			"bworld:stone"
+		],
+		[
+			-1,
+			99,
+			1,
+			"bworld:stone"
+		],
+		[
+			-1,
+			99,
+			2,
+			"bworld:stone"
+		],
+		[
+			-1,
+			99,
+			3,
+			"bworld:stone"
+		],
+		[
+			0,
+			99,
+			-3,
+			"bworld:stone"
+		],
+		[
+			0,
+			99,
+			-2,
+			"bworld:stone"
+		],
+		[
+			0,
+			99,
+			-1,
+			"bworld:stone"
+		],
+		[
+			1,
+			99,
+			-3,
+			"bworld:stone"
+		],
+		[
+			1,
+			99,
+			-2,
+			"bworld:stone"
+		],
+		[
+			1,
+			99,
+			-1,
+			"bworld:stone"
+		],
+		[
+			2,
+			99,
+			-3,
+			"bworld:stone"
+		],
+		[
+			2,
+			99,
+			-2,
+			"bworld:stone"
+		],
+		[
+			2,
+			99,
+			-1,
+			"bworld:stone"
+		],
+		[
+			3,
+			99,
+			-3,
+			"bworld:stone"
+		],
+		[
+			3,
+			99,
+			-2,
+			"bworld:stone"
+		],
+		[
+			3,
+			99,
+			-1,
+			"bworld:stone"
+		],
+		[
+			0,
+			99,
+			0,
+			"bworld:stone"
+		],
+		[
+			0,
+			99,
+			1,
+			"bworld:stone"
+		],
+		[
+			0,
+			99,
+			2,
+			"bworld:stone"
+		],
+		[
+			0,
+			99,
+			3,
+			"bworld:stone"
+		],
+		[
+			1,
+			99,
+			0,
+			"bworld:stone"
+		],
+		[
+			1,
+			99,
+			1,
+			"bworld:stone"
+		],
+		[
+			1,
+			99,
+			2,
+			"bworld:stone"
+		],
+		[
+			1,
+			99,
+			3,
+			"bworld:stone"
+		],
+		[
+			2,
+			99,
+			0,
+			"bworld:stone"
+		],
+		[
+			2,
+			99,
+			1,
+			"bworld:stone"
+		],
+		[
+			2,
+			99,
+			2,
+			"bworld:stone"
+		],
+		[
+			2,
+			99,
+			3,
+			"bworld:stone"
+		],
+		[
+			3,
+			99,
+			0,
+			"bworld:stone"
+		],
+		[
+			3,
+			99,
+			1,
+			"bworld:stone"
+		],
+		[
+			3,
+			99,
+			2,
+			"bworld:stone"
+		],
+		[
+			3,
+			99,
+			3,
+			"bworld:stone"
+		],
+		[
+			1,
+			100,
+			0,
+			"bworld:chest"
+		],
+		[
+			2,
+			100,
+			0,
+			"bworld:furnace"
+		]
+	],
+	"tiles": [
+		{
+			"id": "bworld:chest",
+			"x": 1,
+			"y": 100,
+			"z": 0,
+			"data": {},
+			"containers": {
+				"main": [
+					null,
+					null,
+					null,
+					null,
+					{
+						"id": "bworld:coal",
+						"count": 6
+					},
+					null,
+					null,
+					null,
+					null,
+					null,
+					null,
+					null,
+					null,
+					null,
+					null,
+					null,
+					null,
+					null,
+					null,
+					null,
+					null,
+					null,
+					null,
+					null,
+					null,
+					null,
+					null
+				]
+			}
+		},
+		{
+			"id": "bworld:furnace",
+			"x": 2,
+			"y": 100,
+			"z": 0,
+			"data": {
+				"progress": 50,
+				"progress_max": 200,
+				"fuel": 751,
+				"fuel_max": 1000
+			},
+			"containers": {
+				"main": [
+					{
+						"id": "bworld:iron_ore",
+						"count": 2
+					},
+					{
+						"id": "bworld:coal",
+						"count": 2
+					},
+					{
+						"id": "bworld:iron_ingot",
+						"count": 1
+					}
+				]
+			}
+		}
+	],
+	"players": {
+		"alice": {
+			"x": 0.5,
+			"y": 100,
+			"z": 0.5,
+			"yaw": 0,
+			"pitch": 0,
+			"selected_slot": 0,
+			"inventory": [
+				{
+					"id": "bworld:coal",
+					"count": 2
+				},
+				null,
+				null,
+				null,
+				null,
+				null,
+				null,
+				null,
+				null,
+				null,
+				null,
+				null,
+				null,
+				null,
+				null,
+				null,
+				null,
+				null,
+				null,
+				null,
+				null,
+				null,
+				null,
+				null,
+				null,
+				null,
+				null,
+				null,
+				null,
+				null,
+				null,
+				null,
+				null,
+				null,
+				null,
+				null
+			]
+		}
+	},
+	"entities": [],
+	"mod_storage": {}
+}
diff --git a/tests/helpers.ts b/tests/helpers.ts
index 194a20f..44da9b4 100644
--- a/tests/helpers.ts
+++ b/tests/helpers.ts
@@ -25,6 +25,7 @@ export function mod_sources(mods_dir: string): ServerModSource[] {
 			},
 			data: {
 				blocks: mod.blocks.map((b) => b.json),
+				models: mod.models.map((m) => m.json),
 				items: mod.items.map((i) => i.json),
 				recipes: mod.recipes.map((r) => r.json),
 				ores: mod.ores.map((o) => o.json),
diff --git a/tests/mod_loading_test.ts b/tests/mod_loading_test.ts
index c793797..33cd616 100644
--- a/tests/mod_loading_test.ts
+++ b/tests/mod_loading_test.ts
@@ -3,7 +3,6 @@ import { AIR, CHUNK_HEIGHT } from "$/common/constants.ts";
 import { BlockRegistry, EverythingRegistry, ItemRegistry } from "$/common/everything_registry.ts";
 import { block_from_json, block_to_json, item_from_json, item_to_json } from "$/common/mod_data.ts";
 import { generate_raw_chunk } from "$/common/generation.ts";
-import { get_state_value } from "$/common/utils.ts";
 import { load_worldgen } from "$/common/worldgen_loader.ts";
 import { create_mod } from "$/tools/new_mod.ts";
 import { PROTOCOL_VERSION } from "$/common/protocol.ts";
@@ -35,37 +34,6 @@ Deno.test("the base game loads from mods/bworld", async () => {
 	assert(EverythingRegistry.get<ItemRegistry>("items", "bworld:watering_can")?.on_create);
 });
 
-Deno.test("bone meal grows wheat until it's fully grown", async () => {
-	const { game, take, send } = await test_game("mods");
-	game.on_connect(1);
-	send(1, { type: "hello", name: "alice", protocol: PROTOCOL_VERSION });
-	send(1, { type: "ready" });
-
-	let y = CHUNK_HEIGHT - 1;
-	while (game.world.get_block_nid(1, y, 1) === AIR) y--;
-	y += 1;
-	game.set_block(1, y, 1, "bworld:wheat");
-	const wheat = EverythingRegistry.get<BlockRegistry>("blocks", "bworld:wheat")!;
-	const age = () => get_state_value(game.world.get_block_value(1, y, 1), wheat, "age")!;
-	assertEquals(age(), 0);
-
-	send(1, { type: "chat", text: "/give bworld:bone_meal 8" });
-	const slot = inventory_of(take(1)).findIndex((i: Msg) => i?.id === "bworld:bone_meal");
-	send(1, { type: "select_slot", slot });
-	send(1, { type: "move", x: 2.5, y, z: 2.5, yaw: 0, pitch: 0 });
-
-	// 2 to 5 stages at a time
-	send(1, { type: "use_block", x: 1, y, z: 1, face: "top" });
-	assert(age() >= 2 && age() <= 5, `age ${age()}`);
-	// at most 3 more uses to reach 7, then it stops using bone meal
-	for (let i = 0; i < 5; i++) send(1, { type: "use_block", x: 1, y, z: 1, face: "top" });
-	assertEquals(age(), 7);
-	const left = inventory_of(take(1))[slot]?.count;
-	assert(left >= 4 && left <= 6, `${left} bone meal left`);
-	// nothing got placed on top
-	assertEquals(game.world.get_block_id(1, y + 1, 1), "bworld:air");
-});
-
 Deno.test("mods/bworld json survives going to the registry and back", async () => {
 	await test_game("mods");
 	for (const file of Deno.readDirSync("mods/bworld/blocks")) {
diff --git a/tests/server_scripts_test.ts b/tests/server_scripts_test.ts
index f322d5c..0135eb5 100644
--- a/tests/server_scripts_test.ts
+++ b/tests/server_scripts_test.ts
@@ -24,6 +24,28 @@ export function setup(ctx: ServerContext) {
 		on_tick() { throw new Error("broken on purpose"); },
 		on_click(block, _params, player) { log("click", [block.id, player.name]); },
 	});
+	// a box that only takes coal, counts how often it's opened, and gives up its items when broken
+	ctx.components.register_block("testmod:coal_box", {
+		on_interact(block, _params, player) {
+			block.data ??= { container: ctx.containers.create(2).id, opened: 0 };
+			block.data.opened += 1;
+			const screen = ctx.ui.open_container(player, {
+				container: ctx.containers.get(block.data.container)!,
+				layout: [{ slot: 0, x: 0, y: 0, filter: (item) => item.id === "bworld:coal" }, { slot: 1, x: 1, y: 0 }],
+			});
+			screen.set_property("opened", block.data.opened);
+			screen.on_close(() => log("closed", screen.open));
+			return true;
+		},
+		on_break(block) {
+			const container = ctx.containers.get(block.data.container)!;
+			for (let slot = 0; slot < container.size; slot++) {
+				const item = container.get(slot);
+				if (item) ctx.world.drop_item(block.x, block.y, block.z, item);
+			}
+			ctx.containers.delete(container.id);
+		},
+	});
 	ctx.components.register_item("testmod:wand", {
 		on_use(item, params: { power: number }, player) { log("use", [item.id, params.power, player.name]); },
 	});
@@ -84,6 +106,10 @@ function test_mods() {
 		`${mod}/blocks/broken.json`,
 		block("testmod:broken", { components: { "testmod:broken": {} } }),
 	);
+	Deno.writeTextFileSync(
+		`${mod}/blocks/coal_box.json`,
+		block("testmod:coal_box", { interactive: true, components: { "testmod:coal_box": {} } }),
+	);
 	Deno.writeTextFileSync(
 		`${mod}/blocks/lamp.json`,
 		block("testmod:lamp", {
@@ -227,3 +253,50 @@ Deno.test("/tps reports the loop, and mods can't take engine commands", async ()
 	assert(error.includes("/tps belongs to the engine"), error);
 	Deno.removeSync(clash, { recursive: true });
 });
+
+Deno.test("container screens: filters, properties, closing, saving, and dropping what's inside", async () => {
+	const { game, send, take, log, dir } = await setup();
+	game.set_block(1, 100, 0, "testmod:coal_box");
+	send(1, { type: "chat", text: "/give bworld:coal 3" });
+	send(1, { type: "chat", text: "/give bworld:stone 1" });
+	take(1);
+
+	send(1, { type: "use_block", x: 1, y: 100, z: 0, face: "top" });
+	let messages = take(1);
+	const opened = messages.find((m) => m.type === "open_screen");
+	assertEquals(opened.layout, { rows: 1, slots: [{ index: 0, x: 0, y: 0 }, { index: 1, x: 1, y: 0 }], bars: [] });
+	assertEquals(messages.find((m) => m.type === "screen_properties").properties, { opened: 1 });
+
+	// stone doesn't go into the coal slot, but does into the other one. coal goes in
+	const screen = (messages: { type: string; container?: string; items?: unknown[] }[]) =>
+		messages.filter((m) => m.type === "container" && m.container === "screen").at(-1)?.items;
+	send(1, { type: "click", container: "inventory", index: 1, button: 0 });
+	send(1, { type: "click", container: "screen", index: 0, button: 0 });
+	send(1, { type: "click", container: "screen", index: 1, button: 0 });
+	send(1, { type: "click", container: "inventory", index: 0, button: 0 });
+	send(1, { type: "click", container: "screen", index: 0, button: 0 });
+	messages = take(1);
+	assertEquals(screen(messages), [{ id: "bworld:coal", count: 3 }, { id: "bworld:stone", count: 1 }]);
+
+	send(1, { type: "close_screen" });
+	assertEquals(log().closed, [false]);
+
+	// the items and the block's data are saved
+	const loaded = await test_game(dir, game.save());
+	loaded.join(1, "alice");
+	loaded.send(1, { type: "move", x: 0.5, y: 100, z: 0.5, yaw: 0, pitch: 0 });
+	loaded.send(1, { type: "use_block", x: 1, y: 100, z: 0, face: "top" });
+	messages = loaded.take(1);
+	assertEquals(screen(messages), [{ id: "bworld:coal", count: 3 }, { id: "bworld:stone", count: 1 }]);
+	assertEquals(messages.find((m) => m.type === "screen_properties").properties, { opened: 2 });
+
+	// breaking it closes the screen, runs on_close, and drops what was inside
+	loaded.send(1, { type: "break_block", x: 1, y: 100, z: 0 });
+	assert(loaded.take(1).some((m) => m.type === "close_screen"));
+	const logged = loaded.game.mods.storage.testmod.log as Record<string, unknown[]>;
+	assertEquals(logged.closed, [false, false]);
+	const dropped = loaded.game.item_entities().map((e) => e.item.to_data().id).sort();
+	assertEquals(dropped, ["bworld:coal", "bworld:stone"]);
+	assertEquals(loaded.game.containers.size, 0);
+	Deno.removeSync(dir, { recursive: true });
+});