Well made simple platformer.
Only things I would change are making it so you can double jump while already moving upwards. (My inputs have been eaten one too many times .-.)
And making the hurtbox slightly smaller than the actual slime sprite. Games like this can feel unfair even when the hitboxes are accurate so giving leeway makes it more satisfying in my opinion.
Overall though a good game, I'll definitely check out other games you've made. Well done!