Polyominoes

Polyominoes are 2-D geometric shapes made by "gluing" squares together along their edges.

Dominos are one example. The well-known game of Tetris uses tetromino shapes.

Polyominoes generally do not count designs that are a reflection or flip of another shape.

Tetrominoes: 5 arrangements

Pentominoes -- how many arrangements?
Hexominoes -- how many arrangements?
How can you be sure you have found them all?

Extension questions:
     Symmetry and reflection
     Sequences
     Tessellations & tilings
     Polyiamonds
     Soma cubes