These are the rules as included with the X version.

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There are 72 tiles, two of each combination of six colors and six shapes.
At the start of the game, there are six tiles on the board representing
each shape and color.  To place an additional tile on the board, you
must match at least one adjacent tile according to the following rules:
   - To match a single tile, you must match either the color or shape.
   - To match two tiles, you must match one shape and one color.
   - To match three tiles, you must match two colors and one shape OR two
     shapes and one color.
   - To match four tiles, you must match two colors and two shapes.

Tiles placed on the interior (lighter) squares score points when placed,
according to the number of adjacent tiles that they match.
   - Matching one tile:    1 point.    - Matching three tiles:  4 points.
   - Matching two tiles:   2 points.   - Matching four tiles:   8 points.

In addition to the regular score there is an increasing bonus for each
four-way match starting with 25 points for the first and continuing with
50, 100, 200, 400, 600, 800, 1000, 5000, 10000, and 50000 points.

A bonus of 1000 points is awarded at the end of the game placing for all
72 tiles.  500 and 100 points are awarded for one and two tiles remaining.