Digital circuitry causes 10 LEDs to light sequentially back and forth and emits a "click" at the end of each "swing".  Watch the interesting effect as the lights sequence rapidly through the middle and slow down at the ends just like a mechanical metronome.

Components:  5 resistors, potentiometer, 5 capacitors, 4 diodes, 10 LEDs, 2 transistors, 5 ICs, speaker, battery snap, slide switch

Principles taught:  digital logic, counters, multiplexers