please keep in mind that for the earlier levels you wont have to complete the whole thing. just get enough to the point where you kill entire waves extremely easily and then save up the rest of you're money. you'll earn more points and get more skill points this way.
nice game, i found it hard at first but now i dont see what everybody is complaining about. people have posted good tips in the comments. all you have to do is look back a few pages in the comments and you'll be a master of this nice little game.
anyway heres my tactic, its the same on every level:
1) 2 riflemen fully upgraded first.
2) then get $200 and get an electric tower. upgrade it to full. then wait until youve got enough for another one and upgrade that to full.
3) repeat 2 but with machine gunners instead of electric.
4) get 1 sniper and fully upgrade it.
5) from now on get as many heat ray towers as needed.
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