Is it the one that's on a Möbius strip? For anyone interested, if you glue a disc to the (only) edge of a Möbius strip (used in chridd's One side, One jump), you get the real projective plane used in this game. You can't do so in 3D space without self intersections, but that's a minor detail.
Thanks for your feedback! While turning being slow has already been mentioned, it's really useful to know how many people found this an issue compared to other things, so thanks for that! Difficulty is a bit unbalanced, I think there's some difficulty spikes, level 4 is probably one.