Built a very simple square wave oscillator controled by a photocell. Aka, a phototheremin
or optotheremin.

I cased it into a “amp” that came with part of a toy guitar. The plans needed a small
speaker and AA batteries, which it already had, so that worked out well.

The light sensitive part is in the far top left of the front. Aka, where the input jack
would be if it were a real amp. It can use it’s internal speaker, or the 1/4 inch jack
mounted on the left. Sounds pretty insane though a fuzz/step phaser/delay.

Also fun to turn the lights out, and “play” it with a flashlight.

Aka, what I did instead of watching the war.