Nice platformer game, but the controls and hitboxes are a little janky.
When i hold left/right and press UP, it rarely registers it. I get stuck on sides of things quite often and also "hang" on side of a platform.
The hang on side bug pretty much looks like what I dealt with in my game where if i mirrored the player sprite it'd miscalculate the hitbox or something and let me hang on right side of a platform.
I fixed that by instead of flipping the sprite, i swap the sprite for a mirrored one.
It looks like this was made in GMS 1. You can check Shaun Spalding on youtube. He has qute a lot of GMS 1 tutorials. :)