The 13 square Wang tiles are designed so that they tile the infinite plane, but only in an aperiodic (non-repetitive way). Such sets of tiles are very rare and therefor worth exploring.
For more details on the background and history of the Wang tiles see the history text.

Each Wang tile has 4 coloured sides. Adjacent tiles must have the same colour at their common edge. The tiles cannot be rotated.

There are two ways to play this game:

• FIT mode (botton at top left border shows 'FIT' text):
  If you click the board, the computer will place a fitting piece.
  If the position is occupied, the computer will place the next fitting piece for this place.
  If the set of fitting pieces is exhausted, you will not be able to click this position anymore. In this case you might have to take a few moves back or use the SELECT-mode described below:
• SELECT mode:
  Click one of the 13 sample tiles at the left border. The selected tile will appear at the top left. You can now place this tile anywhere on the board, if it fits according to the coloured-edge rule.
  To reverse to FIT, simply click the top left button again.

The variants consist of two groups:
Variants 1-n : fill a square, use each tile as often as you like.
Variants 2-n : Here you can use each tile only once. These variants do not have a Solve button, but they have solutions associated with them (click Help/ShowSolution).

Please note that there are three piece sets available.