It has lots of potential, if you ever develop it further...
I was confused by the description, I was expecting a game where user can switch at will real-time between TD and FPS.
But you have to survive the tower defense phase, only if you do then it switches to FPS ("try to escape your own fortress while finding your way through the maze"). I kept running out of the 30 ammo, the gun range is very limited, and hitting the turret weak spots doesn't work most of the time. But anyway you can cheat by jumping over the arena border and walking outside.