This is really fun! But I've come across a bug thats basically softlocked me into the first stage? In easy mode despite having the correct answer (double checked by looking at playthroughs), The game wont confirm that its correct: (screenshot of issue below, hidden for spoilers.
Oh shoot--yeah, that is definitely and error and I haven't seen it before. Could I ask for your save file? If you're on Windows, I believe it should be at C:\Users\[your username]\AppData\Roaming\Godot\app_userdata\Deductopia\savegame.save.
(PS You're not locked out of any content though--all 3 tutorial rooms can be accessed from the map at any time. The remaining rooms are locked in the tutorial.)