It's a really cool game! I like it a lot!
If you want some improvement, you can make better collision box (sometimes I've been stuck against a wall, so I think you can make round corner for squares. That will increase the fluidity and the speed feeling!). You can also give points if the player take a chest with 3 lives, that will lead the player to a more risky gameplay. And finally, you can add a sort of timer for the combo count, like a fade effects or an additive instruments that follow the music, or also increase the speed of the music !
Well, you can do a really good game on that, with levels, weapon and many things !!!
I will follow you to see others improvement !