// ── Arduino Mega 2560 — Three-LED Chase Pattern ──────────────────────────────
// Uses pins 22, 23, 24 — the "Mega-only" digital header.
// Demonstrates that all 54 digital pins behave identically for basic GPIO.
// ─────────────────────────────────────────────────────────────────────────────

const int LEDS[]   = {22, 23, 24};
const int NUM_LEDS = sizeof(LEDS) / sizeof(LEDS[0]);
const int STEP_MS  = 200;   // Time each LED stays lit

void setup() {
  for (int i = 0; i < NUM_LEDS; i++) {
    pinMode(LEDS[i], OUTPUT);
  }
  Serial.begin(9600);
  Serial.print("Arduino Mega 2560 — using ");
  Serial.print(NUM_LEDS);
  Serial.println(" LEDs on pins 22-24");
}

void loop() {
  // Forward chase: 22 → 23 → 24
  for (int i = 0; i < NUM_LEDS; i++) {
    digitalWrite(LEDS[i], HIGH);
    delay(STEP_MS);
    digitalWrite(LEDS[i], LOW);
  }

  // Reverse chase: 24 → 23 → 22
  for (int i = NUM_LEDS - 1; i >= 0; i--) {
    digitalWrite(LEDS[i], HIGH);
    delay(STEP_MS);
    digitalWrite(LEDS[i], LOW);
  }

  // All on briefly as a separator
  for (int i = 0; i < NUM_LEDS; i++) digitalWrite(LEDS[i], HIGH);
  delay(STEP_MS * 2);
  for (int i = 0; i < NUM_LEDS; i++) digitalWrite(LEDS[i], LOW);
  delay(STEP_MS);
}