// There are 4 buttons, 4 associated LEDs, and 4 MP3 players

const int PinIn[] =   {A0, A1, A2, A3}; // Input pins connected to buttons
const int LEDPins[] = {12, 8,  5,  2};  // LED pins for each button
const int PWMPins[] = {11, 9,  6,  3};  // PWM pins for each MP3 module

bool timer(int index) {static unsigned long data[3][2] = {{0,300000},{0,1000},{0,2000}};
          if (millis()-data[index][0]>data[index][1]){data[index][0]=millis();return true;}return false;}
          
void setup() {
  for (int i = 0; i < 4; i++) {
    pinMode(PinIn[i],   INPUT_PULLUP); 
    pinMode(LEDPins[i], OUTPUT); digitalWrite(LEDPins[i], HIGH);  // 12v LED powered by buck converter with enable pin
    pinMode(PWMPins[i], OUTPUT); analogWrite (PWMPins[i], 0);}    // short tiny pulse will activate the MP3 module
    for (int j=0;j<30;j++){for (int x=0;x<4;x++){digitalWrite(LEDPins[x],HIGH);delay(40);digitalWrite(LEDPins[x],LOW);delay(20);}}}

void loop() {if (timer(0)) {dobutton(random(4));} // play a random MP3 every 5 minutes
             for (int group=0;group<4;group++){if (digitalRead(PinIn[group])==LOW) {dobutton(group);}}}

void dobutton(int z) {analogWrite(PWMPins[z],1); delay(20); analogWrite(PWMPins[z],0);
     for (int j = 0; j < 30; j++) {digitalWrite(LEDPins[z], HIGH);delay(30); digitalWrite(LEDPins[z],LOW); delay(30);}}