Actually kinda fun! I tried it a bunch of times and didn't complete it, but I don't usually try something more than once if I don't enjoy it, and I'm not usually a fan of platformers either. The basic premise is really engaging and the mechanic is well executed. The flashing is a lot to look at though - and my eyes kept darting from the timer at the top, back to where the action was. Maybe making the player pulse instead of the background, and keeping the timer near the player, would ease the fatigue on the eyes. The color palette is also pretty sharp - it's clear and easy to read, which is good - but the clashing primary colours are hard on the eye too. Maybe check out coolors and try some of the palettes there? I don't think the game needs sprites, but animating the player with a little bit of squash and stretch might be nice, and pretty easy. I really like that there's different ending messages depending on how far you got; that's a really nice touch. Don't take the criticism to heart if you're happy with where the game is at; for something made in such a short amount of time, it's good fun :)