Chemotactic Nanorobot Tumor Homing (2D)

This is the 2D counterpart to the 3D chemotactic nanorobot scene, computing the identical run-and-tumble chemotaxis — a swarm of medical nanorobots swimming down a blood-vessel segment toward a tumor by biasing a random walk on a sensed chemical gradient, without ever sensing the gradient's direction. Each robot only measures whether the local chemoattractant concentration is rising or falling while it swims, extending straight runs during a rise and tumbling to a fresh random heading during a fall, so the swarm nets a statistical drift toward the tumor purely from that temporal bias. Tune the gradient's reach, the swarm's chemotactic sensitivity, its population and the thermal/flow noise it swims through, then watch live readouts track how many robots dock and release their drug payload, how long that takes, and the swarm's net drift speed.