//#1 LED Blinks to say Get Ready
//#2 Random OFF time for LED
//#3 LED ON SOLID and you press the button
// Your reaction time is calculated and printed to the Serial Monitor in milliseconds

#define LED_PIN     12
#define BUTTON_PIN  2
#define BLINK_LED   5
uint32_t reactionTime, startTime, previousTime = 0;
bool ledState = 1, blink = 1;
uint16_t randomCount, count;

uint16_t getRandomVal(void){
  count = 0;
  return random(6, 21);
}

void falling(void){
  uint32_t pressMillis = millis();
  detachInterrupt(0);  
  calculate(pressMillis);
}

void calculate(uint32_t pressTime){
  reactionTime = pressTime - startTime;
  Serial.println((String)"Reaction Time: " + reactionTime + "mS\n");
  blink = true;
  return;
}

void setup() {
  Serial.begin(9600);
  pinMode(LED_PIN, OUTPUT);
  digitalWrite(LED_PIN, ledState);
  pinMode(BUTTON_PIN, INPUT_PULLUP);
  randomSeed(A0);
}

void loop() {
  if(millis() - previousTime >= 500){
    count++;
    if(!blink){
      if(count >= randomCount){
        ledState = HIGH;
        startTime = millis();
        count = 0;
      }
    }else{
      ledState = !ledState;
      if(count >= BLINK_LED){
        blink = false;
        randomCount = getRandomVal();
        attachInterrupt((0), falling, FALLING);
        ledState = LOW;
      }
    }
    digitalWrite(LED_PIN, ledState);
    previousTime = millis();
  }
}