The last 40 levels of Perfect Balance, as we know it. Balance all the given shapes, and don't let them fall off the screen.
A and D (or cursor keys left and right, or mouse wheel when it works) rotate the selected shape. W and S rotate in very small steps. Use mouse for the rest.
A context menu should be shown when right-clicking or, on touch devices, long-pressing in the game. This menu especially allows to play in full screen and control the volume.