Great simple platformer. Love the art, especially being your first game that's pretty impressive. It works, it's fun to play, not much to complain about with this one.
My only critiques are largely just small things that could be tweaked to offer a little bit of a better experience. The jump is really high and a bit jarring at first and the horizontal movement speed makes some of the platforming a bit tough but that's really it. Nothing serious or hugely detrimental to the game, great job.