This is fun! I'm impressed by how much you made out of a very simple mechanic.
I wish the rules of movement were slightly better communicated/defined. I figured out that getting a running start makes you go higher pretty early, but the movement sometimes felt a bit unintuitive.
Also, you might be aware, but the spike kill boxes are a bit too small in places. I saw the spike animation but didn't die a number of times.
I do love the little shadow visual effect on the player. It makes a visual style that's basically "oops all orange" look really slick!