oh... that's a nice little play-kit there :D

at first I got a bit hyped because it looked like a full on modular synth :P

let me see what you have wired up there?! A photo-resistor and an led, the led has a current limiting resistor and seems to be driven from a relay. The relay is properly wired with the fly-back diode and triggered from a transistor... that's where things get mysterious, without seeing the "controls" off to the left side, I'd have to guess it's a light-triggered LED with an override switch?!