#include <LiquidCrystal.h>

// button
const int buttonpin = 4;
int Button_state;

// Display
int rs = 12;
int en = 11;
int d4 = 10;
int d5 =  9;
int d6 =  8;
int d7 =  7;
LiquidCrystal lcd(rs, en, d4, d5, d6, d7);

// LED
const int redled = 6;
const int greenled = 5;
int led_state;

// Other
unsigned long randomnumber;
unsigned long reaction_time;

void setup() {
  // put your setup code here, to run once:
  pinMode(buttonpin, INPUT_PULLUP);
  pinMode(greenled, OUTPUT);
  pinMode(redled, OUTPUT);
  Serial.begin(9600);
  lcd.begin(16, 2);

  lcd.setCursor(0, 0);
  lcd.print("Reaction time:");
  lcd.setCursor(0, 1);
  lcd.print("Press to begin");
  digitalWrite(redled, HIGH);

  digitalWrite(redled, HIGH);
  digitalWrite(greenled, LOW);
}

void loop() {
  // put your main code here, to run repeatedly:
  led_state = 0;
  Button_state = digitalRead(buttonpin);
  Serial.println(Button_state);

  if (Button_state == 0) {
    led_state = 1;
    digitalWrite(redled, LOW);
    lcd.clear();
    lcd.setCursor(0, 0);
    lcd.print("Wait for the");
    lcd.setCursor(0, 1);
    lcd.print("green light");
    randomnumber = random(3498, 5782);
    delay(randomnumber);
    digitalWrite(greenled, HIGH);
    reaction_time = millis();
    led_state = 1;
  }

  if (Button_state == 0 && led_state == 1) {
    lcd.clear();
    lcd.print(reaction_time);
  }
}