An good first game! I have some comments but it is for sure something to be proud of. The style is lovely and I like the use of colour. You have a lot of foundational stuff down already
- Transition between levels - it's a little jumpy at the moment
- Fall deaths, have the camera stop and let the player fall past the camera
- Fewer Invisible walls! Let me run free!
- Look at the parallax layer option for background
- I think an enemy stop halt when it kills you
- Instead of telling me to jump over a gap, use coins to entice me
- It looks like you implemented fast fall and jump buffer but I'm not certain about coyote time?