Regardless of whether it's totally original, it's impressive from a coding standpoint and just a fun game. 5/5. After all, there aren't that many great games that are 100% original - this is a formula that works.
The full version is one of the best Flash games I've ever seen, even if it is pretty easy. The guns, especially the rifle, were fun to use, and the ability to blow holes in walls was surprisingly helpful/realistic. 5/5 for the full version!
Even without being that good at it (or not having enough luck), I'm still totally hooked. Only 2 problems I see: The one life part is kinda annoying, and also once you click a powerup (i.e. bomb) there's no way to put it back without using it. All in all, though, a great game, and I'd kill to have it on my iPod :D