A solid platformer.
Would be cool if starting/restarting the game could be done by pressing A since your controls already has both my hands on the keyboard.
After taking a hit you are almost guaranteed to get hit a second time right after - could add some invincibility time before I can get hit a second time.
Level 4 is too unforgiving with just one try at jumping enemies for second key. Enemies there could use some respawn system.