Thank you so much for taking the time to try it! I'm sorry you couldn't make whirlpools. :/ maybe your circles were too small or too big? 'under the hood' as it were, the play area is a grid of 16x16 pixel spaces, every time a trail spawns all it's neighbor spaces 2 away in the 4 cardinal directions check if they're surrounded by trails in all 4 cardinal directions (2 away) & there are no other whirlpools in that range (this check includes diagonals). So if your trails were all in a single grid space you wouldn't spawn one, or if they were more than 5 grid spaces apart from one another it also would not spawn one. I originally tried to have the spawning check also check diagonals, but that made it so whirlpools were spawning any time you turned and made like an "L" shape.
Anyway, thank you for saying it seems fun even if you didn't really get to play it, lol! I hope you have a wonderful day and good luck in the Jam!