Refactor

backend/src/physics/functions/force-at-position.ts

@@ -1,9 +1,10 @@
 import { vec2 } from 'gl-matrix';
+import { exertsForce } from '../../objects/capabilities/exerts-force';
 import { Physical } from '../physicals/physical';
 
 export const forceAtPosition = (position: vec2, objects: Array<Physical>) =>
   objects.reduce(
     (sum: vec2, o: Physical) =>
-      !o.canMove ? vec2.add(sum, sum, o.getForce(position)) : sum,
+      exertsForce(o) ? vec2.add(sum, sum, o.getForce(position)) : sum,
     vec2.create(),
   );