For higher levels (when the riflemen do all the work): use 2 Quake box and 1 laser tower. Don't buy the old glory, because later on the game you'll need a heavy weapon (I recommend the Space Laser) and just a fast secondary weapon for blowing up the nuke trucks (with the S.C.A.R. you'll be fine). Al level 25-30 start buying repair men, you will need them, he.
 "Storm the House 3"){kind=icon}
 "Vector Conflict: The Siege"){kind=icon}
 "Save the Snail"){kind=icon}
 "Busman 3D"){kind=icon}
 "Starship Commander"){kind=icon}
 "Goin Up"){kind=icon}