To follow up on the other reply, a match entails practically any arrangement of same-color blocks that connect with each other on the horizontal / vertical axes and form a closed shape. A two-by-two square is the simplest arrangement, but it could also be a three-by-three square, a two-by-three rectangle, or any form of abstract polygon... just so long as they're comprised of the same color and you can draw a continuous line from any one block in the circuit back to itself by following the path you build.
