Easy way to get 5k.
Go on sewer, large option. Get a rebound gun, stock up on ammo, and sit in the corner of the mid-right platform. Lay on the ground, and you can shoot thru the floor.
Course, that's just me. ^^
I like how the turret will either auto kill the enemy, or wait until they hit your fort 2-20 times, and then shoot.
Bad game imo. Wouldn't recommend it.
The game itself was pretty cool, but it had to many hints (walkthrough was unneeded). I'd like to play another one of these, but without the circles telling me what to do. ^^