Very simple rules, what you see at the beginning will carry you through the entire game. The only added mechanic (from lvl 37 onward) is one-way pathways.
I’m just past half way through the game (100 levels total) and all the levels were done in one (most), two (few) or three (very few) quick attempts; all except three random levels which took me a couple dozen tries each. So either the game’s difficulty progression is unbalanced, or my brain is (very likely).
I didn’t care for the story either, so I’m done with the game.
It has almost exclusively great reviews though, so maybe it’s something special for the puzzle lovers. I don’t know.
PS it’s on Steam as well (not free tho).
