The concept for Stack City was to create a system that would make minimal use of sensing and the circuitry involved in it. Our goal was to build a robot that would use stationary mechanical systems to manipulate blocks into known positions, from which they could easily be moved.

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The main idea was to have a roller and shovel deploy into the block depot and collect a block as the robot moved along the side. With sufficient spin of the roller and forward driving force from the robot, a block was virtually guaranteed to land in the shovel. Once a block was collected, the robot would lift the block partway up the shovel's wall and retract the roller and shovel, then head immediately back to the build zone. At the build zone the shovel and roller walls would be redeployed around an existing stack to align and protect it. The carried block would then be lifted to the top of the shovel wall, where it would be ejected by a wedge and fall down the chute created by the two walls to land on top of the existing stack.