const int red = 2;
const int yellow = 8;
const int green = 12;
const int button = 6;

int redInterval = 10000;
int yelInterval = 2000;
int greenInterval = 15000;

int currTime = 0;
int prevTime = 0;

int counter = 0;

void setup() {
 
  pinMode(6, INPUT);
  pinMode(2, OUTPUT);
  pinMode(8, OUTPUT);
  pinMode(12, OUTPUT);
  Serial.begin(9600);
}

void loop() {
  
  currTime = millis() - prevTime;

  if (digitalRead(button) == HIGH){
    if (currTime < 5000){
      greenInterval = 20000;
      redInterval = 5000;
    }
    else if (currTime < redInterval){
      greenInterval = 20000;
    }
  }
  
  if (counter == 0){
    digitalWrite(red, HIGH);
    if (currTime > (redInterval)){
      digitalWrite(red, LOW);
      counter = 1;
    }
  }
  else if (counter == 1){
    digitalWrite(green, HIGH);
    if (currTime > (redInterval + greenInterval)){
      digitalWrite(green, LOW);
      counter = 2;
    }
  }
  else if (counter == 2){
    digitalWrite(yellow, HIGH);
    if (currTime >= (redInterval + greenInterval + yelInterval)){
      digitalWrite(yellow, LOW);
      counter = 0;
      prevTime = millis();
      currTime = 0; 

      greenInterval = 15000;
      redInterval = 10000;
    }
  }
}