Fig 1Power-up vending machineCoin, code, then grab and toss itcredit 0 · sensor ready
The coil that is turning, the display and the header signNine spiral coils, three per shelf, each driven by a motor at the backInfrared drop sensor across the bin: it must see the item fallInsert a coin and the display shows your credit. Type a row letter and a column number, or tap a slot. Its motor turns the spiral coil one full turn, which moves every item forward by one pitch (the gap between two loops), so the front item rolls off the shelf. As it falls it breaks the infrared beam across the drop zone. That is how the machine knows you got it: if the beam stays unbroken, a real machine turns the coil again or gives your money back. Push the flap to take the power-up, then grab it and toss it around: once you pick it up, its fuse is lit, and a few seconds later it bursts into its effect.