Add basic multiplayer

backend/src/physics/physical-game-object.ts

@@ -0,0 +1,10 @@
+import { GameObject } from 'shared';
+import { BoundingBoxBase } from './bounds/bounding-box-base';
+
+export interface PhysicalGameObject extends GameObject {
+  getBoundingBox(): BoundingBoxBase;
+  //distance(target: vec2): number;
+  readonly isInverted: boolean;
+  readonly canCollide: boolean;
+  readonly canMove: boolean;
+}