Objective: Defend your Barracks against 30 waves of random enemies.

Press the button in the Factory to begin the map. Yes, you can exploit this by researching everything before starting the map. Go ahead, do it, I don't care. It only takes one impatient person to foil your plan, though.

Hint #1: Schedule upgrades in the Research Lab to make defending easier.
Hint #2: Repair structures with the wrench to survive longer.