Minimal Autonomous Cleaning Robot, cleans the floor powered by electro motor vibrated brush and navigating randomly. It has no brain, so no risk it will take over the world. It is easy and cheap to build, inspired by the toothbrush based bristlebot. My 2 sons B. (11y) and E. (14y) each built one.
Cleaninator : Autonomous Cleaning Robot : it can clean even difficult spaces :