For secret level 13, finish level 12, go back to the title screen, then select New Game.
Love the changes you made since the last version. Keep up the excellent work!
I wouldn't say the hard leves are "easy" but they do seem easier than the so-called medium levels. Or maybe the player just gets better at thinking about how to use your past selves to solve problems as the game goes on.
At first I thought it was too easy and repetitive, but after the first few levels, it gets challenging. The difficulty ramps up perfectly. Also, the names given to the different patterns give it a nice artistic touch.
Hope this gets badges.
WarEmblem's comments