In this game you have to delete all colored (red, green and blue) blocks. You can do this in two ways. You can make them land on a transparent block of the same color. There has to be a black or grey field underneath, otherwise the colored block will fall down and your attempt will fall through. You can also move the colored block to an orange star, and make it disappear into nothingness. You can move the grey blocks as you like, in order to support the colored blocks.
Use the arrow keys to move the blocks. Use Z to undo something and do a step back.