diff --git a/packages/ecs/src/Component.ts b/packages/ecs/src/Component.ts
index e8c20f9..bf5bdbe 100644
--- a/packages/ecs/src/Component.ts
+++ b/packages/ecs/src/Component.ts
@@ -14,6 +14,11 @@ class Component {
     init(properties: NonNullable<object>) {
         this.properties = properties;
     }
+
+    // Use this when saving the state.
+    serialize(): NonNullable<object> {
+      throw new Error(`You need to implement this for ${this.constructor.name}`);
+    }
 }
 
-export default Component;
\ No newline at end of file
+export default Component;
diff --git a/packages/ecs/src/Entity.ts b/packages/ecs/src/Entity.ts
index cd05df0..f793904 100644
--- a/packages/ecs/src/Entity.ts
+++ b/packages/ecs/src/Entity.ts
@@ -66,6 +66,9 @@ export default class Entity {
   }
 
   public hasComponent(declaration: typeof Component): boolean {
+    if (typeof declaration.prototype.bitmask === "undefined") {
+      throw new Error(`Please register the component ${declaration.name} in the ComponentRegistry.`);
+    }
     return hasBit(this.componentsBitmask, declaration.prototype.bitmask);
   }
 
diff --git a/packages/renderer/src/canvas.ts b/packages/renderer/src/canvas.ts
index a653795..8d1bcd6 100644
--- a/packages/renderer/src/canvas.ts
+++ b/packages/renderer/src/canvas.ts
@@ -127,7 +127,7 @@ export function dot(ctx: CanvasRenderingContext2D, x: number, y: number, fillCol
   ctx.restore();
 }
 
-export function rectangle(ctx: CanvasRenderingContext2D, x: number, y: number, width: number, height: number, strokeColor: string = "black", fillColor?: string): void {
+export function rectangle(ctx: CanvasRenderingContext2D, x: number, y: number, width: number, height: number, strokeColor: string = "rgb(0,0,0)", fillColor?: string): void {
   //ctx.save();
   ctx.beginPath();
   ctx.lineWidth = 1;