Prototype RGB FaderJack
Fun introduction to simple circuits involving potentially complex variables. Works with common cathode AND common anode RGB diodes, but pinout as well as code is different for each type.
The only way to tell the difference between a common cathode and a common anode diode is... it will either work, or not work. Multiple ways it can partially but not fully work. Fun to troubleshoot.
The code fades from red to blue to green through all internet colors in between. Fun to put a ping pong ball, practice golfball (whiffle ball type), or drinking straw over the LED.