The charging mechanic was really fun and creative. I had a lot of fun playing through it! The music and art also lent themselves really well to the steampunk aesthetic. One minor point that I would mention is that the levels difficulty is very front loaded, as, as far as I could tell, the enemies don't progress in any way other than speed. I always found myself struggling for the first minute on a level before I got my upgrades, then once I did the levels became significantly easier, despite the speedup mechanic
All in all, a very creative game with a great art direction!