Two sets of colored balls, labeled A through D, sit in a box as shown below. Your job is to move the red balls to the red zone and the blue balls to the blue zone.
Sound difficult? It gets harder. Within each zone, all the balls must stay in their correct ABCD order in order for you to complete the puzzle.
Balls can only move into vacant spots, and they can't jump over other balls.
Your first priority should be to get all the balls switched over to their matching zones.
Once you've moved the balls to their correct zones, you can worry about arranging them in the proper order.
You are going to have to be a little methodical in your approach to this puzzle.
You can stumble upon the answer by just moving things around, but the puzzle is much easier to finish when you create rules for yourself to operate by.
Make sure you aren't just repeating the same unsuccessful moves each time you start moving balls around.
It's easy to move balls around without thinking, but that'll get you nowhere. Remember to stay focused on your goal when moving things around. The truth is that experimenting with the puzzle is more useful than any hint you could get, but since you paid for it, here's one more.
You have very little room to work with. As you've probably figured out, there's a single spot in the center where you can stash a ball, so make good use of it.