All cheats for this game by platform:
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Shipyard and Factory Capacity
In the ship build window, when you choose a planet to build on, the shipyard and factory capacity of that planet will be shown next to the factory and shipyard capacity needed for the ship you're building. If the shipyard and factory capacity is less than that of the ship you are building, it will take more than one turn to build. Moral: Shop around for planets to build things on.
Technology
After the initial turn you'll have very little money left over. You'll want to immediately hike your tax rate to 15-20%. You always want to pump up technology. I devote 1/4 Ð 1/3 of my surplus to technology. I hold off allocating anything to espionage until I actually encounter another race. If population is getting to be a problem I increase social spending. This also has the benefit of allowing me to increase taxes even higher, but decreases the productivity of your factories and shipyards. I always allocate 100% to fleet and 100% Ð 200% to colonies depending on how fast I want them to grow.
Alternate between high and low tax levels
Once you've built an adequate number of ships for current needs, stop building ships altogether, and concentrate on Research & Development until your technology levels have gone up by about four to six in each category (weapons and shields particularly). When you're ready to replace the worst of your ships, bring the tax rate down and replace a whole class. Then crank the rate back up. A reasonably productive homeworld can build a fair-sized squadron in three turns with a low tax rate.
Efficient construction
If the ship you are building is larger than the factorys capacity, then its construction will take more than one turn. So before you build your ship, shop around. Each planet differs in shipbuilding ability.