/*
 * Arduino UNO Traffic Light Control System
 * MakeMindz.com — Beginner Embedded Systems Tutorial
 *
 * Simulates a real traffic signal using 3 LEDs:
 *   Green LED  → Pin 3 → GO      (5 seconds)
 *   Yellow LED → Pin 2 → SLOW    (2 seconds)
 *   Red LED    → Pin 1 → STOP    (5 seconds)
 *
 * Each LED is connected via a 220Ω current-limiting resistor.
 * Total cycle time: 12 seconds (repeating)
 */

const int greenPin  = 3;   // Green LED → Digital Pin 3
const int yellowPin = 2;   // Yellow LED → Digital Pin 2
const int redPin    = 1;   // Red LED → Digital Pin 1

void setup() {
  // Configure all LED pins as digital outputs
  pinMode(greenPin,  OUTPUT);
  pinMode(yellowPin, OUTPUT);
  pinMode(redPin,    OUTPUT);
}

void loop() {

  // ── Phase 1: GREEN — Vehicles GO ──────────────────
  digitalWrite(greenPin, HIGH);    // Turn green ON
  delay(5000);                       // Hold for 5 seconds
  digitalWrite(greenPin, LOW);     // Turn green OFF

  // ── Phase 2: YELLOW — Vehicles SLOW DOWN ──────────
  digitalWrite(yellowPin, HIGH);   // Turn yellow ON
  delay(2000);                       // Hold for 2 seconds
  digitalWrite(yellowPin, LOW);    // Turn yellow OFF

  // ── Phase 3: RED — Vehicles STOP ──────────────────
  digitalWrite(redPin, HIGH);      // Turn red ON
  delay(5000);                       // Hold for 5 seconds
  digitalWrite(redPin, LOW);       // Turn red OFF

  // Cycle restarts automatically — loop() repeats forever
}