With only four days to go until the launch of Apple’s App Store, which will feature 3D games that push the iPhone to its limits, most developers would consider releasing a browser-based iPhone game a bad idea. Throwing common sense to the wind, ad agency Hello Viking has just released Viking Smackdown, a Safari-based iPhone game that manages to take advantage of the phone’s built-in accelerometer. You can access the game by visiting VikingSmackdown.com from your iPhone’s browser.

The game itself is very simple: your goal is to make a cartoony-looking viking throw his axe as far as possible. Tilt your phone to the side and you are presented with a meter that indicates how forcefully you’ll throw your mighty blade. Then, once the meter is full, tilt the phone right-side up to send the axe flying. The farther it goes, the better.

While there have been a number of motion-sensing apps made for “jailbroken” (i.e. hacked) iPhones, few Apple sanctioned web-apps can make use of the phone’s accelerometer. Using some clever scripting, Viking Smackdown takes advantage of the web browser’s orientation detection to create this simple (but surprisingly fun) game. It’s a shame it will be totally obsolete in less than a week.