I'm glad you liked it! X being skip bothers me a lot too. It was a debug command which I left in by mistake. The second to last puzzle was intended to be the hardest level in the first stage before a new mechanic is introduced, but sadly I didn't have time to make more difficult levels using the red dungeon locks.
That level was also harmed by a bug introduced in the last patch before the code was locked - the golden locks aren't supposed to break the key upon unlocking, but the dungeon lock rules somehow infected them too. Well done solving it anyway; it took me a good moment as the designer to see if it was still possible!
It's good to know that level 2 is a good tutorial. Looking back it's a lot cleaner than level 1 and should definitely be first.
Thanks for all your feedback!
-O