add client side terrain without collision

src/game.js

@@ -8,10 +8,12 @@ export default class Game {
 
   #entities = []
   #eventEmitter = new EventEmitter()
+  #terrains = []
   #tickBudget = Math.floor(1000 / this.tickRate)
 
   get entities() { return this.#entities }
   get eventEmitter() { return this.#eventEmitter }
+  get terrains() { return this.#terrains }
   get tickBudget() { return this.#tickBudget }
 
   spawn_entity(entity) {
@@ -19,10 +21,15 @@ export default class Game {
     entity.game = this
   }
 
+  add_terrain(terrain) {
+    this.#terrains.push(terrain)
+  }
+
   state() {
     return {
       ...this,
       entities: this.#entities.map((e) => e.state()),
+      terrains: this.#terrains.map((t) => t.state()),
     }
   }