Total Annihilation lvl 6 (against Core):
Got some time and finished the level. The trick was to spit on defense whatever the briefing says, just build a shipyard, resource-production, and kill stuff with the commander (meanwhile making submarines as units) discovering the preset enemy ships by radars.
lvl 7 is annoying: the computer is superior in technology in every sense. They still not have a base, so there is no hope of preemptive strike.
lvl 8: annoying level where you can't have a base (again), and must protect 3 ships constantly: the ranger (the only thing what can kill stuff now, too expensive to replace any time), the commander (puts down radars) and a repair ship to fix the commander.
As you shoot things from out-of-view the level is particularly stupid, as you should preserve a certain object. Guess how you find which.
lvl 9: finaly something quick: you do what the briefing say: build the airport, build the carrier, fly over and capture in peace. Easy-peasy.
lvl 10: again you only need the commander and a repairbot. Did I mention the builder-bot can create missile-towers what I found the only solution against the aircraft-nuisance?
lvl 11: Initially you are weak on metal, so you'll need a bunch of Metal Maker (produces metal from energy). Always go to the weakest of resistance, and where you find something cool (metal, geothermal energy) build a minibase with anti-aircraft towers (missile towers if you forgot). Then repair your commander and send it out to the new direction.
lvl 12: same as the previous, but in a resource-rich world.
lvl 13: annoying level because the enemy is plentyful and you can't reach it on foot. You must as soon as possible make a solid base to counter enemy aircraft. Then as fast as possible you must reach the border at the middle as clearing the enemy units massing there can turn impossible otherwise. Metal production is a problem on the level, and the advanced constructors worth practically nothing aside building advanced construction-sites. You NEED advancad ariport, two of it to produce a massive amount of aircraft (let them be stealthers) to be able to defend a landing-position for your commander on the other side of the border.
Oh, and don't even dream being able to shoot the enemy from safe distance by some big guns. That won't work.
lvl 14: build some solar plant to cover your immediate energy-need, build a couple metal plant to cover your immediate metal-need, then build a bot-plant to make a constructor which makes a geothermal plant so you have more energy then you'll ever need.
Next is toi make some advanced constructors to make some moho mines and make 2-3 advanced air-plant where you make stealthers which'll guard your commander who'll destroy everything.
Oh, as the Zeus is just another enemy unit, don't even dream about capturing it. Not that it'd effect anything.
lvl 15: you only have the commander, and a survivor unit runs in too. The "meteor shower" is just in beta-phase, so aside the initial one it won't happen. IMPORTANT: turn shooting to Hold Fire! Not many enemies, so if you built 4-5 solar plant you'll have enough energy to shoot the D-gun.