This is really good! I had trouble on the second double jump but after reading some comments I was able to figure it out. My feedback would just be to add the basic platformer stuff:
- Coyote time. Allow the player to jump for just a couple milliseconds after they leave a platform, so it doesn't feel like the game just ignored their jump input.
- Jump buffer. If the player hits the jump key milliseconds before they actually hit the ground, the game should still let them jump.
- have the colliders of deadly stuff be a little bit smaller than the sprites, so that if you just barely brush against something dangerous, it won't hurt you.
- Give the player a material with no friction so they can't weirdly stick to walls or anything.
For a first game, this is very good! Excellent job!