This a simple but challenging puzzle app thats well worth the 99 cents. The pro version apparently includes the ability to download additional levels, but at the rate Im going I wont need that "pro" feature for a long time! I first tried this on my iPhone, but found that the screen was too small to move the blocks accurately, no matter which "tapstyle" I tried. I was getting so frustrated with all the wrong moves I was accidentally making that I almost threw my phone across the room. I then switched to my iPad, and have had no problems whatsoever using the "push" tapstyle to move blocks.