Lovely graphics and animations! Got a bit confused about what background tiles the cart would collide with at first. Difficulty picks up considerably in level 2, there's a number of different obstacles and mechanics to manage and be decent at all of a sudden. The game is fairly short, though, so all in all, the challenge seems right.
Do you plan to continue working on this?
And have you thought of a multiplayer mode? While I was playing, I felt like the game would really lend itself well to multiplayer co-op, possibly without too much additional coding. Feels like it would be a ton of fun sharing this arcade experience with friends and family.