This would be an amazing way to teach JavaScript. Things like Scratch or PencilCode are absolute nonsense. This game is the sort of thing we need to see in education.
That said, it's very free-form and massively scoped. Would probably do better with additional limitations early on, then slowly introduce the user with more power as they go.
Also, audio would have been neat. Playing with that would have been awesome. But I'm an audio guy, so maybe I'm biased. :P