Much like tetris, blocks fall from the top of the screen, and you can move them sideways until they land on something. However, these blocks all consist of two squares, each labelled by a number from 0 to 7. Your aim is to line up three squares, horizontally or vertically, which sum to 7. Alternatively you may arrange three 7's horizontally or vertically. These blocks will then disappear, and anything above them will fall down. You lose when no more blocks will fit on the screen.
Dropping a single block may eliminate more than one triple. You will score 10 points for the first triple, 20 for the second, 30 for the third and so forth. Moreover a triple of 7's scores double points. At the bottom of the screen you can see the next block that will appear, the current speed in blue, and your score in yellow. The controls are below. I suggest using your mouse to play; the block will move horizontally to follow your cursor.
| Key | Effect |
| Left/A | Move the block to the left |
| Right/D | Move the block to the right |
| Down/S/Mousebutton | The block moves down faster; saves waiting. |
| Up/Q/Mousewheel | Rotate the block counterclockwise |
| E/Mousewheel | Rotate the block clockwise |
| P | Toggle Pause |
You might notice that the numbers don't appear equally often. The only ways of writing 7 as a sum of 3 nonnegative integers are:
