diff --git a/app/ecs/systems/integrate-physics.js b/app/ecs/systems/integrate-physics.js
index 0e51b98..837ef8b 100644
--- a/app/ecs/systems/integrate-physics.js
+++ b/app/ecs/systems/integrate-physics.js
@@ -10,8 +10,8 @@ export default class IntegratePhysics extends System {
 
   tick(elapsed) {
     for (const {Position, Forces} of this.select('default')) {
-      Position.x += elapsed * (Forces.impulseX + Forces.forceX);
-      Position.y += elapsed * (Forces.impulseY + Forces.forceY);
+      Position.x = Position.$$x + elapsed * (Forces.$$impulseX + Forces.$$forceX);
+      Position.y = Position.$$y + elapsed * (Forces.$$impulseY + Forces.$$forceY);
     }
   }