And to most of the missions the strategy is to build 1 big power generator, 1 Autogun turret just in case and then spam fighter bays (50 en) building Interceptors (75 en) 'till you win. Upgrade: energy generators then fleet production speed, rocket and bullet damage, building and turret armor, then ship's weapons and armor and everything else. With the facility that speeds ship construction up by 50% the rest of the game is a piece of cake, including the last mission.
Also you can build while the game is paused.
Last mission solution (ofc your fighters and buildings need be fully upgraded): build two big power generators, 1 research lab for faster production and ~10 fighter bays with fighters (75 en each). Then accumulate energy and build another research center to spam fighters faster. Then you can relax and build capital ships like supercarriers. Easy peasy.
So, you can actually beat the game with just 1 fully upgraded spy (I got another one for a substitute) and a rocket unit to destroy the entire level after hostages and stars are collected. Spy's agility and invisibility allows to gather all the 'items' and then it's just a question of DESTROY F*CKIN' EVERYTHING WITH EFFIN' ROCKETS!!!
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