Not bad
Pretty nice little game, there was a few little gripes that could be easily addressed to make it a more enjoyable experience i think.
I think the main gripe was that the jump was too sticky, like some levels the percision level is highly dependent on sharp button presses. Whether its the keyboard or mouse button the jump lagged a bit to trigger. So I dont think its a performance issue, i think it just needs to be programmed tighter.
Artwise, it looks fine, but nothing really that memorable. The character, I feel you could have given a bit more personality to. Just looks kind of generic. Like even with the primitive graphics engine that Commander Keen had, you could still easily distinguish him as Commander Keen and not just a generic boy.
So yea that was my two gripes. I liked the simple concept and I agree that it would work well as a mobile port.