int redPin = 13;
int ylwPin = 9;
int btnPin = 2;

int state = 1; // 1, 2, 3, 4
int old_state;

bool isButtonPressed;
bool btn_val, old_btn_val;

unsigned long currentTime;
unsigned long lastTime;

void setup() {
  pinMode(redPin, OUTPUT);
  pinMode(ylwPin, OUTPUT);
  pinMode(btnPin, INPUT_PULLUP);
}

void loop() {
  currentTime = millis();
  readButton();

  switch(state) {
    case 1:
      if (isButtonPressed) {
        state = 2;
      }

      if (currentTime - lastTime > 3000) {
        state = 3;
      }

      ledControl(0, 0);
      break;
    
    case 2:
      if (isButtonPressed) {
        state = 3;
      }

      if (currentTime - lastTime > 1000) {
        state = 1;
      }

      ledControl(1, 0);
      break;

    case 3:
      if (isButtonPressed) {
        state = 4;
      }

      if (currentTime - lastTime > 1000) {
        state = 2;
      }

      ledControl(0, 1);
      break;

    case 4:
      if (isButtonPressed) {
        state = 1;
      }

      if (currentTime - lastTime > 1000) {
        state = 3;
      }

      ledControl(1, 1);
      break;
  }

  if (state != old_state) {
    lastTime = currentTime;
  }
  old_state = state;
  
}

void ledControl(bool redState, bool ylwState) {
  digitalWrite(redPin, redState);
  digitalWrite(ylwPin, ylwState);
}

void readButton() {
  btn_val = !digitalRead(btnPin);

  if (btn_val && !old_btn_val) {
    isButtonPressed = true;
  }
  else {
    isButtonPressed = false;
    delay(50);
  }

  old_btn_val = btn_val;
}