Pretty good game. Simple idea but with a lot of room to explore. The level design is good, it has a good difficulty progression, introduced spikes after some levels, etc.
Graphics and music are also on point. I would love to listen to the gameplay music more, only while fighting level 10 I got a glimpse of the rest of the song.
The only critique I have is that the jump to start triggering jump was not the best. In the first few levels I felt that it was just unnecessary. Then after some levels it was setup to be the correct thing to do, but then level 10 arrived and the jump at the start is actually the wrong thing to do.. It's a pretty small detail, but if you're forcing the player to do some action try to make it always the correct action.
Good job making it, I have loved it!