Your effort shows, for sure. You have talent for making interesting stuff!
When switching from how to play, credits, etc., the various pages will overlap each other.
The level 1 shift to the end of the map really threw me off since gameplay was still active. The leaves me unable to see what I doing, where to jump, etc. Luckily, it went back to the birdy before I fell to my death, so I was able to figure out how to get across the chasm. Something similar happened in level 3 and it was a wild guess on where to jump.
At level 2, the background does this weird where the entire BG shuffles and shifts depending on the player's position on the map. It is most notable after jumping down and trying to go between the first two trees. I also way overshot the exit with the bird. :D