Use the Arrow Keys or the WASD keys to move the Boxmen to the floating cube on each level. 

Use the Shift key to create Boxmen - they are copies of yourself that continue doing the action you were doing when you created them. For example, if you stand and press shift, they will stand at the place where you made them. But if you're moving or jumping, the Boxmen will copy that action. 

You can see the limit for how many Boxmen clones you can make in the top left corner. You don't need to keep your blue boxmen alive - as long as any of your boxmen reach the cube, you'll win the level!

If you get stuck, press R to restart.