I built a rear bike light and attached it to the back of a bike shirt. It has 4 modes: off, on, blinking, and scrolling. The modes are controlled by 4 switches, placed in separate locations around the shirt. This was done instead of toggling on a single switch because if you’re wearing the shirt you can’t actually see the light, so you wouldn’t have any feedback as to which mode you are in. The light is made up of 36 red LEDs set into 6 rows. Each row is controlled by a separate digital output pin. Each switch is read by a separate digital input pin. The whole thing is run off of a 9V battery. I’ve attached two schematics, one for the inputs and one for the outputs. I’ve also attached the code.