diff --git a/packages/topdown/layer.js b/packages/topdown/layer.js
index c7ba1da..2b7194b 100644
--- a/packages/topdown/layer.js
+++ b/packages/topdown/layer.js
@@ -1,3 +1,6 @@
+import * as I from 'immutable';
+
+import {EntityList} from '@avocado/entity';
 import {Tiles} from '@avocado/topdown';
 
 export class Layer {
@@ -5,7 +8,8 @@ export class Layer {
   constructor() {
     this.tiles = undefined;
     this.tilesetUri = undefined;
-    this.entityList = undefined;
+    this.entityList = new EntityList();
+    this._state = I.Map();
   }
 
   fromJSON(json) {
@@ -18,4 +22,15 @@ export class Layer {
     return this;
   }
 
+  get state() {
+    return this._state;
+  }
+
+  tick(elapsed) {
+    if (this.entityList) {
+      this.entityList.tick(elapsed);
+      this._state = this._state.set('entityList', this.entityList.state);
+    }
+  }
+
 }
\ No newline at end of file