'Monochro Observer' is a simple puzzle game. The aim is to take the two players to the gray-colored goal. A White man can walk in the Black world, and a Black man can walk in the White world.

Key Control
[Left & Right] : Move player
[Shift] : Switch player
[Z] : Generate / Remove a block at player's feet
[X] : Rewind your play
[C] : Reset stage
[S] : Return to the Stage Select
[1] : Return to the Title
[M] : Toggle mute mode