I am trying to get something to work so that an RGB LED fades through the color spectrum, and when a button is pressed some music plays. That is not the problem. Assume I am using any loop that functions can be called at any time in. I am trying to make it so that if the button is not pressed for a certain amount of time, say 30 seconds, the light stops fading through the color spectrum and when the button is pressed in this 'sleep mode', first the light starts fading, and then the next press plays the music. I am aware this could be done somehow with millis();, but how would I approach this? I am using an Arduino Uno.