constexpr unsigned long overallBlinkTime = 10000;
constexpr unsigned long blinkDelay       =  500;
constexpr unsigned long lightDelay       =  500;

constexpr byte buttonPin = 5;

constexpr int noOfLeds = 3;
byte ledPin[noOfLeds] = {2, 3, 4};

int currentLed = 1;
int lastLed = 0;
byte button;

byte step = 0;

unsigned long lastBlinkTime = 0;
unsigned long startOfThisStepTime;


void setup() {
  Serial.begin(115200);
  Serial.println("Start");
  for (int i = 0; i < noOfLeds; i++) {
    pinMode(ledPin[i], OUTPUT);
  }
  pinMode(buttonPin, INPUT_PULLUP);
  randomSeed(analogRead(0));
}


void loop() {
  button = buttonState();

  if (step == 0) {
    if (button == LOW) {
      for (int i = 0; i < noOfLeds; i++) {
        digitalWrite(ledPin[i], LOW);
      }
      while (currentLed == lastLed) {
        currentLed = random(0, noOfLeds);
      }
      lastLed = currentLed;
      digitalWrite(ledPin[currentLed], HIGH);
      step = 1;
      startOfThisStepTime = millis();
    }
  }

  if (step == 1) {
    if (millis() - startOfThisStepTime >= lightDelay) {
      if (button == LOW) {
        step = 2;
        startOfThisStepTime = millis();
      } else {
        digitalWrite(ledPin[currentLed], LOW);
        step = 0;
      }
    }
  }

  if (step == 2) {
    if (millis() - lastBlinkTime >= blinkDelay) {
      lastBlinkTime = millis();
      byte actState = digitalRead(ledPin[currentLed]);
      digitalWrite(ledPin[currentLed], !actState);
    }
    if (millis() - startOfThisStepTime >= overallBlinkTime) {
      digitalWrite(ledPin[currentLed], LOW);
      step = 0;
    }
  }
}

byte buttonState() {
  static unsigned long lastChangeTime = 0;
  static byte lastState = HIGH;
  static byte state = HIGH;
  byte actState = digitalRead(buttonPin);
  if (actState != lastState) {
    lastState = actState;
    lastChangeTime = millis();
  }
  if (state != lastState && millis() - lastChangeTime > 30) {
    state = lastState;
  }
  return state;
}