// Define the pin number where the push button is connected
// Digital pin 2 is used as input from the button
const int buttonPin = 2;

// Define the pin number connected to the LED
// Pin 13 is connected to the onboard LED
const int ledPin = 13;       

// setup() runs only once when the board powers up or resets
void setup()
{
    // Configure LED pin as OUTPUT
    // Control the LED state - send HIGH (5V) or LOW (0V)
    pinMode(ledPin, OUTPUT);

    // Configure button pin as INPUT_PULLUP
    // Internal pull up resistor is enabled

    // This means:
    // Button NOT pressed  -> pin reads HIGH
    // Button PRESSED      -> pin connects to GND and reads LOW
    
    // External resistor is not required in this configuration
    // Button wiring:
    // One terminal -> Pin 2
    // Other terminal -> GND
    pinMode(buttonPin, INPUT_PULLUP);

    // Ensure LED starts in OFF state during initialization
    // LOW removes voltage from LED pin
    digitalWrite(ledPin, LOW);
}

// loop() runs repeatedly after setup finishes
void loop()
{
    // Read current state of button pin
    
    // Since INPUT_PULLUP is used:
    // LOW  = button pressed
    // HIGH = button released
    if (digitalRead(buttonPin) == LOW)
    {
        // Button is pressed
        // Turn LED ON by setting output HIGH
        digitalWrite(ledPin, HIGH);

        // Wait for 250 milliseconds
        
        // This delay:
        // 1. Prevents very fast switching
        // 2. Gives visible LED response
        // 3. Slightly reduces effect of switch bouncing
        
        // Note:
        // delay() blocks processor execution
        delay(250);
    }
    else
    {
        // Button is not pressed
        // Turn LED OFF
        digitalWrite(ledPin, LOW);
    }
}