Now, for the moment you've all been waiting for: the announcement of the contest winners! They were selected at random (by a computer program) just a few minutes ago.
1st prize (appearance/easter egg in full version & a Lemma Soft book):
ozurr
2nd prize (Lemma Soft book):
Unicorn
Congratulations, you two!
Since the contest is over, I will post the solutions to each of the demo levels for those of you who are stuck.

