No AI for War

Killing with Kindness · Module 7 “Hands-on AI” · with Zach Tijhaar

The idea

AI is already used to pick out targets based on how people look. We wanted visitors to feel that, in a light-hearted way. You walk past a webcam, a soap-bubble machine on a turret follows you, and if your shirt is a “target colour” it opens fire. Put your hands up and the bubbles stop.

On the way out a receipt prints with your photo and the message: “You were targeted just because you are wearing a [colour] shirt today; imagine if you were targeted because of the colour of your skin or your religion. We used bubbles, and we stopped when you put your hands up. What if it wasn’t bubbles, what if they didn’t stop? #NoAIForWar”

We deliberately didn’t target black, white or brown, or things like glasses, so the installation never comes close to targeting skin tone or a medical aid.

What I built

• Tracking and targeting: a Logitech C920 webcam with MediaPipe pose tracking. The bubble machine on a pan/tilt turret follows the visitor’s position.
• Hands-up detection: an SVM model on MediaPipe shoulder, elbow and wrist landmarks (scaled, RBF kernel, k-fold cross-validation). It beat a simple “wrists above shoulders” rule on the edge cases.
• Shirt colour: we trained a CNN first, but it overfitted to the yellow room we collected data in. An HSV colour filter inside the torso area from MediaPipe worked far better live, so that’s what we used.
• Hardware: an ESP32 receives servo angles from Python over Wi-Fi (REST). It switches the bubble machine’s rewired trigger through a relay and runs on an external 5V 3A supply. The first 3D-printed turret with MG90S servos couldn’t tilt the machine, so we rebuilt it in wood with bigger servos. A bigger soap tank is connected with aquarium tubing.
• Receipt printer: a thermal printer prints the message and the webcam photo.

Result

It ran as a walk-through installation on demo day. The tracking and ceasefire worked after some calibration. Most people needed to be told to put their hands up, so next time the hint should be part of the experience, not just on the poster.