Yo! Congrats on finishing your first game jam! I think its a pretty good game as its simple & compact, arcade type minigame. I think the choice to vary the timing window was a nice touch to give the gameplay a bit of variety, though I wish it had been taken a bit further by maybe adding multiple yellow windows or something else. I do think it would be nice to indicate to the player when the bar would shift somehow
The game is missing a bit of visual feedback for successful hits and misses, as it is hard to tell how far off I was if I did miss the yellow mark. Adding the visual feedback can also help the game feel more addicting as its easier to attribute the action to a reward.
Game balancing wise I think the multiplier scales too fast to really be a punishment. If the player misses the once they only have to hit yellow 4 times to get back to the top multiplier. The forgiving nature of the scoring and the inconsistent perfect counter makes it more optimal to spam the spacebar key when the bar is not near the edges
The mixels are a little unpleasant (differently sized and scaled pixel art) but I get why it was done that way
BUGS
It does seem like there is a bit of roughness regarding the perfect hits, as there are a good number of times where I would obviously miss the yellow and sometimes even miss the green, but my multiplier would stay at 8
Game continues after death. If the player stays on the you died screen, their score will still tick up and more enemies will spawn (eventually falilng onto the player and re-playing the you died sound effect
Overall I enjoyed my time playing the game, and I hope my critique is helpful!