Beep Melody

You are working the till of a small neighbourhood grocery. Boxes ride the belt towards the scanner, and each one has to arrive barcode up and square to the beam, or it goes past unscanned. Every scan plays the next notes of a melody, locked to the beat of the backing track, so a good shift sounds like a tune rather than a row of beeps. A flip with no wasted moves scores more and plays an extra note. Misses cost the queue's patience — run it out and the shift is over. Seven levels and an endless shift, four backing tracks to choose from, and a short lesson to start with. A warm daytime anime corner shop.