Quad*Doku is a tile word game from Cadaco, designed by Ronald O. Weingartner (a former Hasbro exec) and is not unlike Crossword Squares.

You only form four letter words in a ring along the sides of the square. Each time you get a four letter word whose tile values add up to 10 you get a bonus. Otherwise, you get only the tile values. Tiles stack on other tiles.