Nice.
I really like this game. I'd like to see some new structures if you add another sequel tho ;-)
To the players:
I did ran some tests, and did some maths. Here are the more interresting facts, mostly about energy management.
Solar stations: lvl 2 solar stations are more efficient than lvl 1 and 3. They provide 233 energy per minute (epm) for 400 minerals (m) instead of 100epm for 200m (lvl 1) and 333epm for 600m (lvl 3).
Mineral miners: Lvl 1 and 2 both need 25 energy per minute. That's a hidden cost around 45 minerals (1/9 of a lvl 2 solar station) ... Taking this into acount, a lvl 2 miner is almost 20% more efficient than a lvl 1. As you might have guessed, a solar station lvl 2 is enough to support 9 miners, and you probably won't have much more of them (if they are lvl 2 that is).
Pulsars: When fighting non stop, a lvl 1 needs 70 energy per minute (epm), a lvl 2 needs 200epm, a lvl 3 needs 400epm. To put it another way, one solar station lvl 2 is enough to run 3 of those pulsars at lvl 1, only 1 at lvl 2 and you'll need 2 of those stations to run a lvl 3. Think carefully before upgrading.
THEL: Lvl 1 are really weak, you shouldn't build one if you can't afford the upgrade to lvl 2 quickly after. The upgrade to lvl 3 is worth it too but not as vital. One solar station lvl 2 is enough for a lvl 3 THEL when fighting waves. It gets more expensive against mother ships or other things with lot of HPs, but since your pulsar will most likely be out of range during those fights you shouldn't need additional stations.
Missile Launcher: Each missile cost 5 minerals, all the version have a 10s cooldown, 400 minerals (m) for 1 missile every shot, 900m for 2 and 1900m for 4. Damages increase with level too. Lvl 1 are more efficient against waves while lvl 3 are more efficient against huge ships (only small differences tho).
Conclusion: If you didn't know yet, you can build/upgrade when the game is paused. Doing so and using the above figures you should easly be able to make sure you have enough solar stations. Also, don't forget that to upgrade or build something costs a lot of energy ... Try not to build too many structures at a same time, especialy when fighting.
Khann