ReactionTimer.ino

const int ledPin = 13;
const int buttonPin = 2;

unsigned long startTime;
unsigned long reactionTime;
bool waitingForPress = false;

void setup() {
  pinMode(ledPin, OUTPUT);
  pinMode(buttonPin, INPUT_PULLUP); // Internal pull-up activated
  Serial.begin(9600);
  randomSeed(analogRead(0)); // Seed random delay
}

void loop() {
  Serial.println("Get ready...");
  delay(2000); // Wait before starting

  int randomDelay = random(2000, 5000); // 2–5 seconds
  delay(randomDelay);

  digitalWrite(ledPin, HIGH); // LED ON = press button now
  startTime = millis();
  waitingForPress = true;

  while (waitingForPress) {
    if (digitalRead(buttonPin) == LOW) { // Button pressed
      reactionTime = millis() - startTime;
      digitalWrite(ledPin, LOW);
      Serial.print("Your reaction time: ");
      Serial.print(reactionTime);
      Serial.println(" ms");
      waitingForPress = false;
      delay(2000); // Pause before next round
    }
  }
}