Really addicting. Nice graphics and good gameplay. I'm really enjoying it so far A few small points of attention though:
Bullets don't always bounce off walls correctly, sometimes they just come straight back at you.
(Enemy) bullets sometimes should straight through the corners, I might even have seen a tank moving through there, but I wasn't paying enough attention. I'm probably mistaking.
It's often hard to tell the difference between your own bullets (that hurt everyone) and those of the enemy (that hurt only you)
The slow ready... steady... go... actual go is annoying. It helps get a view of the arena, but you should be able to skip it.
Anyway, nice game.