Nice game!
This one is really fun to play, and I like a creative take on the theme.
I like how throughout the bosses, you eventually learn their patterns and it'll help you know what you need to do within the new loop variant. Especially with the dark modifier, you already know what to expect from the bosses, so its not much of hinderance later on.
The polish on this game is also great, good use of squash and stretch and everything feels very satisfying. For a game in which you don't really do a lot differently content wise, it was still very enjoyable to throw the boxes at the bosses.
Obviously there is a lot of potential here for more designs, either having more bosses that get rotated in, as well as different loop modifiers. I think there would need to be some amount of structure to the fights to make it work outside of a jam, but nothing a little bit of tweaking cant do. Maybe each boss is its own level, but I do like how it switches between the bosses as you go.
You thought of a good idea for a short jam like this, since you can technically just keep adding loops on top of it for as long as you'd like until the time is out, and no matter how many you have the game isn't left any less unfinished.
Letting the player choose to have more health and different assist options is very good, since I think the most important thing to have for a game jam game is the ability for players who want to play your game not get stuck by not being able to. And these are nice additions to a game that can't really give out level skips.
Portrait mode seems to maybe sometimes make the snake one impossible not to take damage? Maybe I'm wrong and just bad at snake, but I think it'll cover the entire wall sometimes and you are forced to walk through.
Made it to loop 5 on my first try, is there anything big I'm missing?
Great work!