I did the 6th challenge a totally different way. I built up some basic collectors around the starting valley until the area was full. Then, I made 4 blasters on the cliff just to the left of the start. When the blasters were done (about the time the creeper was invading), I took the home base and the 4 blasters and invaded the creeper instead, moving to the center upper hill on the bottom, two blasters on each side. Using reactors and only two active blasters (after the initial push, just to keep the two spawn positions inactive), as well as SAMs, I then built up from the mountain and took my revenge ;).
For those complaining about the lasers, don't forget that this game was made with school memories in mind... the hot dogs from the cafeteria would indeed make awesome weapons!
FYI, research does NOT save after you close the game UNLESS you then also purchase an attack upgrade. + to let others know so they don't lose their research too (as I did)!
This game is SO much easier when you realize that you can run into the sand piles to slow down (I thought they'd hurt me until I ran into one by accident).
I got all of the badges/card very easily once I learned the strategy: First, I did get lucky and got an Angel in my first card pack (get one of the expensive ones in order to get some rares). Make one "Super" unit to tank on each of the front squads (if you can, if not, make a column of the strongest possible). Then, in the back, use tons of ranged units: archers, gunners, and mages. Your front will soak up all of the damage and the later groups don't need any armor (just weapon), so they don't take up a lot of army space. I breezed through the missions (including the "hard" 15) and reached 10 in survival mode, all first try.
What I did to get the hard badge in under an hour: Do your best until you get around 1250 starting gold. Then, let your first purchase be max loot (and then second be the 2nd to max loot). This lets you get a ton of cash. After that, I bought the max firepower and flags, eventually trading out the second-best loot upgrade for another flag. I got 48k without TOO much sweat ;).
lol, on 32, I did a single cut and the entire system wigged out, pulling out all of the blocks at once... not that I'm complaining since that meant I got all 3 stars without trying :D!
The key to winning the game is to 100% focus on food production. Food = Population. The forest is the best location to focus on. When you have max food production (or max population while waiting), THEN focus on culture (and lastly production). The tiny production amounts you get at the start of the game don't matter in the end. The real way to win is to build up your population to insane levels and then max out production, getting 1-2k per turn during the final years ;).
For anyone having issues with the final level, here's how I won: Setup: Mage: basic & energy, Warrior: maxed out for tacticians (and fire/energy), General: max lives/cost. Game: I filled up the entire two rows with mages first (no upgrading!). Then, I filled up as much of the upper side as possible with unupgraded warriors. Once the energy teams started, I upgraded as many mages to the 50g upgrade as possible (inflictor won't help). Once they were upgraded, I upgraded both island areas to consecrated energy (since poison will be coming soon). After that, I found the highest-EXP units and made them consecrated fire and focused the last part on making as many powerful tacticians as possible. Remember: Especially at the start, there is power in numbers (and if you don't upgrade them, they won't cause any absorption (although there's no absorption for energy, which is why I focused on it)).
FYI, the "extra scene" in the hard mode is hardly worth it (unless you are doing it for the fun of doing it). It's just the two of them in a green hue hovering over the moon.
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