Age of Wars

http://www.maxgames.com/play/age-of-war.html

Very nicely done game indeed.
At the beginning, it might be hard, but it isn't really.
The last level can be won by only ion-rays.

A guide to beat impossible:
1. wait for enemy to line up and then use special
2. build an egg-automatic
3. keep sending in club-mans so that the enemy doesn't hit base
4. build more egg-automatics as soon as you have enough money (be sure to leave enough for club-mans)
5. DO NOT evolve until the first tank appears. Keep sending in club-mans as fast as you can
6. when the first tank appears evolve to future age and buy