Merry Christmas! (Update v237-7c82c34)

The new update adds a Christmas level and a lot of new music.

Make sure to reset your playlist ("Reset" button in Music menu) so that the new soundtracks show up.

I have to go spend some time with the family so I don't have time to write the list of all fixes that made it into the release.

If there are any critical new bugs you can roll back to "old_version" by right-clicking on the game in the steam game list and choosing "betas" tab, then choosing old_version beta.