
Download the game (392K) or watch a video (spoilers alert, it shows solution for few levels!).
The game is a logic platformer. You control a hero and his alter ego. You have to switch between them to clear a level. It is a bit similar to Binary Land.
This game is a port, or maybe a remake, of recent ZX Spectrum game of the same name. The original version created by Denis Grachev from RetroSouls, you can see video of it here and get it here. NES version got new graphics, original music by Kulor (composed for the game), and some other changes.
Interesting technical feature of this game is that it is written in C, with cc65 compiler. You can get source code here. More details about this and development process in general are available in notes.txt file provided with the game.