The game, called Cosmos Rings, is available right now at a discounted price of $5.99 (£4.49, AU$9.99) as part of a simultaneous worldwide release.
The regular price of the game will be £6.99 (full US and AU prices to be confirmed soon) after August 31.
The game makes use of both the Digital Crown on the watch and the built-in pedometer to drive various gameplay mechanics which include time travel.
So it's reassuring to know that this will not just be a smartphone game scaled down to an even smaller screen.
Whether it's possible to fit a full-scale RPG into the Apple Watch's diminuative size remains to be seen, but we're interested to see what developers end up doing with the device.
- Check out our list of the best Apple Watch apps