Too much too quickly.
One of the main problems this game has is the fact that your opponent gets far too many advancements before you do. For example, on my first run through the game I went for the gold first, then for the oil. After the oil, however, you gave the enemy FUCKING PLANES. This wouldn't be a problem, except for the fact that you have absolutely no way to shoot them down. This, coupled with the fact that funds accrue very slowly even while you're buffing up the rate with the economics building just results in your side being devastated while airstrikes keep coming and units pile up against you.
Unit balance was also an extremely poor aspect of the game. It didn't break it or anything like that, but come on, don't make the Flamethrower's attack range the same as the fucking Sniper's; it defeats the point of the sniper even being different from regular infantry. Also, if you're going to throw in air units that quickly, that can attack the bases directly, you absolutely must give the player some way to defend against it.
I haven't played past the third area, but because of the problems listed above, I have no reason to. You need to balance things like this. Balance the units a bit more, give the player some kind of anti air from the start even if it just shields your bases, and make the money come in a bit faster.
