Hello!
The concept is very nice. I like the art, the music and the overall atmosphere of the game. As other said, diagonal angle makes it unnecessarily hard in my opinion, and I feel that I don't get any reward for this added challenge. I propose to improve the jump as an overall mechanic. It seems I can jump over several sets of spikes with just one jump, so why would I stop in the middle of those spikes? Jump and obstacles should match tight in platformers.
Good job all around!