Billy & Betty bauen

The players have to build together a house with tetris like stones. There is a enigma book. The first stones and the position of 1 or 2 builders is given for each enigma. Also all to be used othercstones are listed. The stones have to be placed 1 by 1 on top of the already placed stones. The buiders are allowed to move, but in maximum 1 stone in height difference. If the buiding has flat surfaces at the end (and matches the size shown by a border line) the team wins.