These things comprise the pieces in the board game   Blokus, and they are also the primary objects controlled by the player in Tetris.
Tomás Oliveira de Silva has enumerated the free types of these things up to order 28, and Iwan Jensen has enumerated their  xed type up to order 56. The  xed type of these things are also known as animals. One of these things which is self-avoiding and convex, as well as containing two adjacent corners of its bounding rectangle, is known as a  stack  one of these things. Two of these things are compatible if there exists a plane  gure which can be tiled by both of them. These things comprise the pieces in the board game   Blokus, and they are also the primary objects controlled by the player in Tetris. For ten points, identify these things consisting of several connected squares.
Tomás Oliveira de Silva has enumerated the free types of these things up to order 28, and Iwan Jensen has enumerated their  xed type up to order 56.
polyominoes