okay guys, start off by building a long link to the bottom of map, and build all power/reserves there, then sell the top few links + solar power.
then build turrets close to each other (so the ranges will be used on both sides effectively), 6 thel's, 2 missles and 4 pulsars should be enough. more thel's if you have extra money.
to beat the darks wave, you got to build 2 level 4 normal towers near the middle, and continue building level 4 normal towers, keep them so creeps can have a path so all towers will shoot tho, e.g. gaps in the middle ;)
Fun game, really easy tho and the ending is very disapointing. Doesn't allow for small mini missions and only allows for the "campaign" as to speak and so spoils it. also annoying how you can't buy missles from the spacestation, considering how you can buy upgrades like extreme havoc etc etc... but was fun :)