Timed events with millis()

//Global Variables
const byte BUTTON=2; // our button pin
const byte LED=13;   // LED (built-in on Uno)

unsigned long buttonPushedMillis;  // when button was released
unsigned long ledTurnedOnAt;  // when led was turned on
unsigned long turnOnDelay = 2500; // wait to turn on LED
unsigned long turnOffDelay = 5000; // turn off LED after this time
bool ledReady = false; // flag for when button is let go
bool ledState = false; // for LED is on or not.

void setup() {
  pinMode(BUTTON, INPUT_PULLUP);
  pinMode(LED, OUTPUT);
  digitalWrite(LED, LOW);
}

void loop() {
  // get the time at the start of this loop()
  unsigned long currentMillis = millis();

  // check the button
  if (digitalRead(BUTTON) == LOW) {
   // update the time when button was pushed
   buttonPushedMillis = currentMillis;
   ledReady = true;
  }

  // make sure this code isn't checked until after button has been let go
  if (ledReady) {
    //this is typical millis code here:
    if ((unsigned long)(currentMillis - buttonPushedMillis) >= turnOnDelay) {
       // okay, enough time has passed since the button was let go.
       digitalWrite(LED, HIGH);
       // setup our next "state"
       ledState = true;
       // save when the LED turned on
       ledTurnedOnAt = currentMillis;
       // wait for next button press
       ledReady = false;
    }
  }

  // see if we are watching for the time to turn off LED
  if (ledState) {
    // okay, led on, check for now long
    if ((unsigned long)(currentMillis - ledTurnedOnAt) >= turnOffDelay) {
      ledState = false;
      digitalWrite(LED, LOW);
    }
  }
}

/* Code Example on how to create virtual delays using Arduino Millis()
** written by James at www.baldengineer.com
**
** For more examples and full explanation visit:
** https://www.baldengineer.com/use-millis-with-buttons-to-delay-events.html
*/