I liked the concept ! I'm interested in how you made the effect when you press P.
Adding a background music and some sound effects may contribute to make your game even better ! If you don't know where to find some musics I suggest you to take a look at Kevin MacLeod for example. For the sound effect you can find free tools to generate sounds like bfxr.
By the way, the game runs fine on Firefox, maybe level loading was a little bit long but we can't do much with web builds ;)
Good job !