diff --git a/packages/physics/src/matter/body.js b/packages/physics/src/matter/body.js
index 0ed745d..73d22b2 100644
--- a/packages/physics/src/matter/body.js
+++ b/packages/physics/src/matter/body.js
@@ -6,9 +6,6 @@ import {
 } from 'matter-js';
 
 import AbstractBody from '../abstract/body';
-import ShapeList from '../shape/list';
-import CircleShape from '../shape/circle';
-import RectangleShape from '../shape/rectangle';
 
 // Translate "real" coordinates to physics coordinates.
 export const SCALE = 1 / 12;
@@ -55,7 +52,7 @@ export default class Body extends AbstractBody {
 
   static bodyFromShape(shape) {
     const shapePosition = Vector.scale(shape.position, 1 / SCALE);
-    if (shape instanceof ShapeList) {
+    if (shape.children) {
       const children = [];
       for (let i = 0; i < shape.children.length; i++) {
         const child = shape.children[i];
@@ -71,12 +68,12 @@ export default class Body extends AbstractBody {
       const {x, y} = body.position;
       return [body, shapePosition, [x, y]];
     }
-    if (shape instanceof RectangleShape) {
+    if (shape.width) {
       const [width, height] = Vector.scale(shape.size, 1 / SCALE);
       const body = Bodies.rectangle(0, 0, width, height);
       return [body, shapePosition, [0, 0]];
     }
-    if (shape instanceof CircleShape) {
+    if (shape.radius) {
       const body = Bodies.circle(0, 0, shape.radius / SCALE);
       return [body, shapePosition, [0, 0]];
     }
diff --git a/packages/physics/src/shape/view.js b/packages/physics/src/shape/view.js
index 0b8fdba..f31941f 100644
--- a/packages/physics/src/shape/view.js
+++ b/packages/physics/src/shape/view.js
@@ -5,25 +5,21 @@ import {
   Renderable,
 } from '@avocado/graphics';
 
-import ShapeList from './list';
-import CircleShape from './circle';
-import PolygonShape from './polygon';
-
 export default class ShapeView extends Renderable {
 
   constructor(shape) {
     super();
     this.container = new Container();
     this.shape = shape;
-    if (shape instanceof PolygonShape) {
+    if (shape.vertices) {
       this.redrawPolygonLines();
       shape.on('aabbChanged', this.onPolygonShapeAabbChanged, this);
     }
-    if (shape instanceof CircleShape) {
+    if (shape.radius) {
       this.redrawCircle();
       shape.on('aabbChanged', this.onCircleShapeAabbChanged, this);
     }
-    if (shape instanceof ShapeList) {
+    if (shape.children) {
       for (let i = 0; i < shape.children.length; i++) {
         const child = shape.children[i];
         const childShapeView = new ShapeView(child);
@@ -36,10 +32,10 @@ export default class ShapeView extends Renderable {
 
   destroy() {
     super.destroy();
-    if (this.shape instanceof PolygonShape) {
+    if (this.shape.vertices) {
       this.shape.off('aabbChanged', this.onPolygonShapeAabbChanged);
     }
-    if (this.shape instanceof CircleShape) {
+    if (this.shape.radius) {
       this.shape.off('aabbChanged', this.onCircleShapeAabbChanged);
     }
     this.shape.off('aabbChanged', this.onShapePositionChanged);