Incredibly fun demo. I love the concept, and it plays very well. In reality I'd say this is worth 3.5 stars, simply because it's also simplsitic (one gun, 4 grenades, no health packs power ups etc). Of course this is just a demo, so I'm looking forward to a full fledged game!
The creator is definitely talented, and I had fun for what little I've played. One caveat however, is that the pointer activates units attack, so if you have your pointer on the edge of the screen, you might get hit by an enemy that you couldn't shoot.