If you asking me better to add a dynamic background 'cause after a short time I was tired from it
For getting the game harder I'll prefer to make some other challengers more than just getting speed up, something like different enemies with different mechanics, dynamic and aesthetics but the main problem is still the visual, specifically the arts (however I'm not an artist, prefer to just talk about the design) but the main idea and the mechanics was good and fun and obviously we see a right scope.