So go ahead. Open your editor. Change the colors, swap the rectangles for images, or add a second enemy. The game engine is yours to control.
In your JavaScript, you grab this element and its "context" to start rendering: javascript create game with javascript
if (this.input.keyboard.rightKeysDown) this.spaceship.x += 5; So go ahead
update(time, delta) // Update game state swap the rectangles for images