const int LED = LED_BUILTIN;
const int BUTTON = PA0;

void setup()
{
    Serial.begin(115200);

    pinMode(LED, OUTPUT);
    pinMode(BUTTON, INPUT_PULLUP);

    randomSeed(micros());

    digitalWrite(LED, LOW);

    Serial.println("Reaction test started");
}

void loop()
{
    // Random LED-off period: 1 to 5 seconds
    int offTime = random(1000, 5001);

    digitalWrite(LED, LOW);
    delay(offTime);

    // Turn LED on
    digitalWrite(LED, HIGH);

    // Measure the first 100 ms
    unsigned long startTime = millis();
    bool fastReaction = false;

    while (millis() - startTime < 400)
    {
        if (digitalRead(BUTTON) == LOW)
        {
            fastReaction = true;
            break;
        }
    }

    if (fastReaction)
    {
        // Fast reaction: LED remains on for 5 seconds
        Serial.println("FAST REACTION!");

        delay(5000);
    }
    else
    {
        // Normal reaction: LED remains on for 1 second total
        unsigned long elapsed = millis() - startTime;

        if (elapsed < 1000)
        {
            delay(1000 - elapsed);
        }
    }

    // Turn LED off
    digitalWrite(LED, LOW);
}