I also made a playthrough of it, if want to see...
We need more waves, the map is too short the way it is now. But we also need respawning ammo and health to deal with more enemies :)
Would be cool if you make the inside shape of the arena change in every wave, to make every fight more unique... like some columns could emerge from the ground after the first wave, then after the second some walls, and then some archs, making some sort of labyrinth, and then some stairs to give more verticality to the fights, and before the last wave a huge temple in the middle could emerge where you can access the exit teleporter after killing the last enemy \o/
i know. i'm tripping balls here, sorry =D