A quick update for anyone who tried it: the first levels have changed. Your first move on level 1 or 2 can no longer end the run without a warning, red marks now simply mean danger, and walls you can hide against have a pattern as well as a colour. If you have ten minutes, we'd love to know whether the start feels fairer now, and which level you stopped on (the LN3- code from the level menu helps a lot).
Game page: https://dohopa.itch.io/the-ribcage (password: ribcage-test)