#include <Arduino.h>

#define LED1 18
#define LED2 19
#define LED3 21

void setup() {
  pinMode(LED1, OUTPUT);
  pinMode(LED2, OUTPUT);
  pinMode(LED3, OUTPUT);
}

void loop() {
  // 1. Alternate Blink
  digitalWrite(LED1, HIGH);
  digitalWrite(LED3, HIGH);
  delay(500);
  digitalWrite(LED1, LOW);
  digitalWrite(LED3, LOW);

  digitalWrite(LED2, HIGH);
  delay(500);
  digitalWrite(LED2, LOW);

  // 2. Gradual Brightness Increase
  for (int i = 0; i <= 255; i += 5) {
    analogWrite(LED1, i);
    analogWrite(LED2, i);
    analogWrite(LED3, i);
    delay(30);
  }
  for (int i = 255; i >= 0; i -= 5) {
    analogWrite(LED1, i);
    analogWrite(LED2, i);
    analogWrite(LED3, i);
    delay(30);
  }

  // 3. Random Blink
  digitalWrite(LED1, random(0, 2));
  digitalWrite(LED2, random(0, 2));
  digitalWrite(LED3, random(0, 2));
  delay(500);
}