// off delay timer

uint32_t timer_preset = 3000; // three second delay
uint32_t current_millis;

const uint8_t pb1 = A0;
const uint8_t led_pin = 5;

uint8_t button_state;

void setup() {
  Serial.begin(115200);
  delay(300);
  pinMode(led_pin, OUTPUT);
  pinMode(pb1, INPUT);

}

void loop() {
  button_state = digitalRead(pb1);

  if (button_state == HIGH) {
    current_millis = millis(); // timer is held reset
  }

  if (millis() - current_millis < timer_preset) {
    digitalWrite(led_pin, HIGH);
  }
  else digitalWrite(led_pin, LOW);
}