In order to solve the puzzle all the boxes need to be pushed to their target destination. You can push any box by taping on it to select it, then tap the target destination. Boxes could be moved anywhere on the board as long as no other box is required to be pushed first. To undo last movement tap or hold on the icon at the top-right part of the screen. To reload the current level tap the icon at the top-left part of the screen.