Racetrax: free iphone ipad puzzle app

How many puzzle apps use an image of a hot girl as part of their icon? There was another puzzle that involved a maze, but I don't recall the title. The object of Racetrax is to swap adjacent tiles to form closed loops. The bigger the loop, the more points you get. After solving level 4, you get a limited time to play level 5. Then you are asked to pay for all the levels. This is a good puzzle! I played it 4 times. You really have to scrutinize the playing board to figure out what swaps will lead to a closed loop. I may even pay the $.99 to keep playing. But there's a problem with this puzzle. I have no idea how the program determines when I'm done with any level before it advances me. Do I get a limited number of moves? Is there a time element? A scoring issue. On that aspect, this puzzle app is a bit frustrating.