Right now, the jumping doesn't feel very good. Here's some ideas:
- Make the ascent faster
- Make the descent 2x as fast as the ascent (Mario falls faster than he jumps! This makes it easier to land precisely where you want to.)
- Give the player more jump height and distance than they need to solve the game's problems (so there's room for error)
- When walking, the player should start and stop instantly, not slide like they're on ice.
- Look into Coyote Time. I couldn't tell if you were using it, because the game has you going up stairs the whole time, but it's an important technique to learn in 2D platformers
I noticed you're using the godot game engine, so here's a video on jumps in godot:
Good luck!