The bonus level is possible. The only way to beat it is to do coyote-jumps. I'm now realizing I should have specified somewere that you can coyote-jump.
Thanks for your feedback! I was thinking of being able to shoot the green projectiles the slimes shoot at you, but I wanted the game to be more harder and stratigic, so I left it as it is.
Really fun game with nice visuals! One little problem was that right when you spawn, and there's an alien on top of the spawn point, then it's an automatic death.
Interesting game, I really like the level design and art! It's a bit hard to know where the fireball is going to land while charging, but overall, it's a fun experience.