There are different endings to this game. In one of the endings all human died, and then in another ending all nations came under the control of the AI.
TOOK ME 3 HOURS TO BEAT LVL 52!!! Here's how you may do it: Put an arrow pointing towards the goal at the left-most corner, then build a elevator of three pieces at the right next to it. Then build a bridge of three bridge pieces and one unit of slope connecting the elevator to the top portal. Then with the remaining piece you'll know how to finish the level =)