This fun little machine built by Youtube's Lamgngo user is a good indication that robots can interact and entertain biological creatures of all kinds. It certainly doesn't hurt that Jerry is a willing accomplice to the repetition of toss and fetch with untiring enthusiasm. The machine seems well thought-out and well-constructed - complete with a microcontroller handling sensor and control functions, plus keeping tally of the toss count. First, a sensor detects the tennis ball's insertion, next the chute raises to the pre-programed angle, then a DC motor pulls back a sling-shot-type contraption along with the ball and lets her fly. Jerry knows exactly what to do including how to load the ball perfectly back into the machine for another round.