Use WASD or the Arrow Keys to roll your blocks and merge with other blocks. Whenever you are touching another block, you'll combine to form a new shape. Make sure to merge in the right order, or else you might get stuck.

You can press Z to undo one move, or press R to restart the level. If you get stuck, you can spend 100 lightning bolts to get the solution by clicking the button in the top right corner. If you run out, complete levels to get more lightning bolts.