You must arrange bricks to form rows without the 'wall' getting too high, or it's game over. You can rotate bricks so that they fit into the wall and once a row is complete it will disappear, thus lowering the wall. Eliminated rows will lower the number of lines you need to complete a level. Bricks fall faster in the higher levels and sometimes there are already bricks in the field that block your path. Often, when you try to make a Tetris four rows of lines that are removed at once, you end up waiting a long time for the long red brick the only way of completing a Tetris. It is interesting to note that every brick is made up of exactly four blocks.