The world is bounded by infinitely long walls to the West and South so robots don't fall off. Walls can be used to represent hurdles, mountains, fences, etc., that robots have to navigate around. Small, plastic cones at intersections that emit a quiet beeping noise. Robots have a bag they can place beepers into and an arm to pick them up and put them down. There can be more than one beeper on an intersection.
Robots can move past beepers easily.
Robot Capabilities Robots can move forward, turn in place. Robots have a TV camera pointing straight ahead that can be used to detect if a wall is blocking the way. Robots can hear beepers that are on the same intersection as the robot. Robots can tell which direction they are facing. Robots have a mechanical arm that can be used to drop and pick up one beeper at a time.