---Details---

Squares go Red -> Orange -> Purple -> Blue (no center)

-> Red -> Orange -> Green -> Purple -> Blue (black center)

-> Red -> Orange -> Purple -> Blue (green center) and then the green center cycle repeats.

Use the arrow keys to select a square and the Z key to manipulate it.

Only red squares can be manipulated.

The game keeps track of your black and green centered squares.

You can try to get the most black or the most green, or whatever you want. There's no built-in objective.