Draw a line traversing an objet to cut it: your goal is to reduce the size of every part as much as possible! When they are enough small they will look yellow, indicating that they are ready to vanish by themselves. You should never cut the black figures, you will not be able to cut the grey ones (they are frozen), the whites will give you more points and the reds are bombs, useful to destroy the grey. Cut all the pieces that you can in the air, because when they touch the ground they turn grey and will fill the space until you lose.
Click and drag to draw a line; the cut happens when you release the mouse button.