Storekeeper

If you don't know Sokoban yet, here are the rules: The objective of the game is to move all the boxes into the green marked goals. You achieve this by pushing the boxes around. Utilize the ARROW keys to push a box in a specific direction, approaching the box from the opposite side. However, the space you intend to move the box into must be vacant. If there’s a wall or another box in the way, you won’t be able to push. Note that you can only push one box at a time, and you can't pull any boxes. A lot of levels are pretty simple (sometimes even obvious), but generally, it becomes tougher with every one you complete. 

Don't worry about finishing all 600 levels in one go. You can always return later and pick up from the level you found tricky or just didn't feel like continuing.