Stairs to descend will spawn.

src/components.ts

@@ -96,13 +96,21 @@ export class Viewshed extends Component<Viewshed> {
 }
 
 /**
- * BlocksTile component.
+ * `BlocksTile` component.
  * Attached to `Entity` that exclusively occupies the space in a map tile from other entities that have the same tag.
  * Initiates `MapIndexingSystem`.
  */
 export class BlocksTile extends Component<BlocksTile> {
 }
 
+/**
+ * `CanDescend` component.
+ * Attached to `Entity` that allows us to descend a level.
+ * Initiates `LevelSystem`
+ */
+export class CanDescend extends Component<CanDescend> {
+}
+
 /**
  * `Attributes` component.
  * Attached to `Entity` that might be in combat to initiate `MeleeCombatSystem`, `HealingSystem`, and `DamageSystem`.

src/level-gen.ts

@@ -1,5 +1,5 @@
 import { Entity, World } from "ecsy";
-import { Rand, Vector2 } from "malwoden";
+import { Rand, Struct, Vector2 } from "malwoden";
 
 import * as Components from "./components.ts";
 import * as Prefabs from "./prefabs.ts";
@@ -56,6 +56,19 @@ export class LevelGenerator {
         return player;
     }
 
+    /**
+     * Get a random position within a specified room `Rect`.
+     * @param room Room `Rect`.
+     * @returns Vector2 Random position in the room
+     */
+    getRandomRoomPosition(room: Struct.Rect): Vector2 {
+        // get a random x and y coordinate
+        const x = this.rng.nextInt(room.v1.x, room.v2.x + 1);
+        const y = this.rng.nextInt(room.v1.y, room.v2.y + 1);
+
+        return { x, y };
+    }
+
     /**
      * Generate a level given configuration information.
      * @param config Map size and game world.
@@ -78,19 +91,21 @@ export class LevelGenerator {
             // choose a creature type
             const creatureType = this.rng.nextInt(0, 100);
             if (creatureType < 50)
-                Prefabs.placeEntity(Prefabs.goblin(this.world), room.center());
+                Prefabs.placeEntity(Prefabs.goblin(this.world), this.getRandomRoomPosition(room));
             else
-                Prefabs.placeEntity(Prefabs.orc(this.world), room.center());
+                Prefabs.placeEntity(Prefabs.orc(this.world), this.getRandomRoomPosition(room));
 
             // create items
             if (this.rng.next() < 0.2) {
-                // get a random spot in the room
-                const randomX = this.rng.nextInt(room.v1.x, room.v2.x + 1);
-                const randomY = this.rng.nextInt(room.v1.y, room.v2.y + 1);
-                Prefabs.placeEntity(Prefabs.bandage(this.world), { x: randomX, y: randomY });
+                Prefabs.placeEntity(Prefabs.bandage(this.world), this.getRandomRoomPosition(room));
             }
         }
 
+        // create stairs in a room that isn't a player room
+        const stairRoomIndex = this.rng.nextInt(1, map.rooms.length);
+        const stairRoom = map.rooms[stairRoomIndex];
+        Prefabs.placeEntity(Prefabs.stairs(this.world), this.getRandomRoomPosition(stairRoom));
+
         return {
             map,
             playerStart,

src/main.ts

@@ -120,6 +120,7 @@ export class Game {
             .registerComponent(Components.Consumable)
             .registerComponent(Components.IncomingHealing)
             .registerComponent(Components.Description)
+            .registerComponent(Components.CanDescend)
 
             // systems - order matters
             .registerSystem(Systems.VisibilitySystem, this)

src/prefabs.ts

@@ -106,4 +106,19 @@ export function bandage(world: World): Entity {
         .addComponent(Components.Description, {
             text: "Will patch up minor injuries."
         });
+}
+
+/**
+ * Create a stairs `Entity`.
+ * @param world Game world object.
+ * @return Entity Stairs `Entity`.
+ */
+export function stairs(world: World): Entity {
+    return world
+        .createEntity()
+        .addComponent(Components.Renderable, {
+            glyph: Glyph.fromCharCode(CharCode.blackDownPointingTriangle, Color.Cyan),
+        })
+        .addComponent(Components.Name, { name: "Stairs" })
+        .addComponent(Components.CanDescend);
 }