const unsigned PatternCountLimit = 500;
unsigned PatternDelays[PatternCountLimit];
unsigned PatternCount = 0;

const byte ButtonPin = 2;
const unsigned DebounceTime = 10;

boolean ButtonWasPressed = false;
unsigned long ButtonStateChangeTime = 0; // Debounce timer

void setup()
{
  pinMode(ButtonPin, INPUT_PULLUP);  // Button between Pin and Ground
  pinMode(LED_BUILTIN, OUTPUT);
}

void loop()
{
  unsigned long currentTime = millis();
  unsigned timeSinceLastChange = currentTime - ButtonStateChangeTime;

  boolean buttonIsPressed = digitalRead(ButtonPin) == LOW;  // Active LOW

  // Check for button state change and do debounce
  if (buttonIsPressed != ButtonWasPressed &&
      timeSinceLastChange > DebounceTime)
  {
    // Button state has changed
    ButtonWasPressed = buttonIsPressed;
    ButtonStateChangeTime = currentTime;

    if (buttonIsPressed)
    {
      // Button was just pressed
      if (PatternCount > 0 && PatternCount < PatternCountLimit)
      {
        PatternDelays[PatternCount++] = timeSinceLastChange;
      }
    }
    else
    {
      // Button was just released
      if (PatternCount < PatternCountLimit)
      {
        PatternDelays[PatternCount++] = timeSinceLastChange;
      }
    }
  }  // End button state change detection

  // Has the button been released for 3 seconds?
  if (PatternCount > 0 && !buttonIsPressed && timeSinceLastChange > 3000)
  {
    // Time to play back
    digitalWrite(LED_BUILTIN, HIGH);
    for (unsigned i = 0; i < PatternCount; i++)
    {
      delay(PatternDelays[i]);
      digitalWrite(LED_BUILTIN, !digitalRead(LED_BUILTIN)); // Toggle
    }
    digitalWrite(LED_BUILTIN, LOW);
    PatternCount = 0;  // reset for new pattern
  }
}