Strategy guide
I am ninja-chickens alt account and I completed the game on impossible here is how:
Keep all the units as the basic ones and just choose stonmason and keep it on that menu throughout. Keep pumping out ogres (special) and those boat things. Also whenever you have enough choose repair from the stonemason.
When your lightning is fully charged you will also need boat full and ogre
Use lightning and then boat with any luck the enmy will then use his lightning then you use ogre. The enwmy will die in seconds. This sometimes needs to be timed right so that the enemy uses lightning etc.
Good luck and have fun kicking this games ass!