If you’re only going to buy one application for your iPhone or iPod touch, it’s got to be this one (at least until I release my own) — because this is something that couldn’t be done in a web app, and it couldn’t be done on your computer screen (actually, it’s adapted from a freeware PC game, but there’s no comparison in the way you play it), and it’s a perfect use of both touch and tilt controls that isn’t a gimmick.

When you read the description, you’ll think it’s just the kind of pretty thing that one has to download just to play once, and to show every friend who doesn’t have an iPhone: there’s a crude wood or stone sculpture in the middle of your screen, and a rope tied to it, and you have to wrap the rope around the sculpture by rotating it. Uh… yeah. (Incidentally, the PC game was originally called “Zen Bondage” but I think I read that the App Store refused found it inappropriate.)

But there are two reasons why you won’t be able to put the game down: First, the art is superb (it’s definitely the most beautiful game on iPhone, even though the 3D models are pretty simple — it’s all about textures and lighting) and the music and sound effects are great (the game starts by saying “designed for headphones,” and it’s absolutely worth plugging them in). Second, the gameplay is the kind with extremely simple rules that develops into complex puzzles that you won’t be able to let go of until you win. I started my first game just before I was going to bed, and ended up sleeping two hours later than I intended. (Fortunately, 3D games drain the battery fast enough that you won’t be able to waste your whole nights, or days, on Zen Bound.)

The good iPhone applications are all about programming to the strengths of the device, and this is exactly what it does. Absolutely worth every cent.

I can’t remember where was the video that made me buy it, but this one is good enough:

Now they need to make downloadable versions for the Wii and PS3.