Stack-22 is a tile-stacking game that uses polyhexes of 5 hexagons, called pentahexes. There are 22 different pentahexes (hence the name of the game). Stack-22 is a new addition to the Pile-Omino family (SEVEN, Pent-Up and Counterplays) by the same designer. All of them play the same, but Stack-22 can be considered a step up from Seven. Warning: this is not a game for the casual player. It is recommended that you at least master SEVEN, Pent-Up or Counterplays before playing Stack-22, as if you don’t know the tactics it can feel a bit cold at the start during the first games. Its depth can be overwhelming (22 opening moves and more than 3000 second moves; the branching factor is crazy), but it rewards those who dare to explore. Summary of gameplay: Players alternate turns placing one of their tiles according to some simple rules, trying to get the most of their pieces on the topmost layers when the game ends. a) The tile must be aligned with the hex grid. b) The selected tile must be placed on the highest level on which it can be placed legally. c) The tile must be placed either on the table and adjacent to a piece already on the table, or atop at least 2 tiles, regardless of their colour. d) The tile must lie flat, with every hex directly supported, either by the table or by a lower tile. —description from the publisher