A member of the community found a bug that breaks the playthrough. As a quick response I rolled back to the last version. However, I cannot reproduce the bug, as it seems to be as rare as Mew.
It seems it has to do with the level generation (by my educated guessing skills), and was most likely not introduced in the last version.
I have made some updates that hopefully negates this a bit, and added a more instructing error screen when it actually occurs. I will continue investigating, but there's not much I can do at this time.
The new version (0.12.1 + the new fixes) will be up again shortly.
Sorry for this messy inconveniance,
Jocce