added flow and basic game

src/Entities/Entity.js

@@ -0,0 +1,9 @@
+
+class Entity {
+  render(ctx: CanvasRenderingContext2D){
+    ctx.fillStyle = 'rgb(200,0,0)';
+    ctx.fillRect(10, 10, 55, 50);
+  }
+}
+
+export default Entity

src/Game.js

@@ -0,0 +1,33 @@
+// @flow
+import type Entity from './Entities/Entity'
+
+const fps = 30
+
+class Game {
+
+  entities: Array<Entity>
+  ctx: CanvasRenderingContext2D
+
+  constructor(_ctx: CanvasRenderingContext2D){
+    this.entities = []
+    this.ctx = _ctx
+  }
+
+  start(){
+    this._draw()
+  }
+
+  _draw(){
+    setTimeout(() => {
+      requestAnimationFrame(() => this._draw())
+      this.entities.forEach(e => e.render(this.ctx))
+    }, 1000 / fps)
+  }
+
+  addEntity(e: Entity){
+    this.entities.push(e)
+  }
+
+}
+
+export default Game