// Pin definitions
const int potPin = A0;      // Potentiometer input

// Signal Pins
const int pin8_Signal = 8;  // Controls NAND 1 (LED 1)
const int pin7_Signal = 7;  // Controls NAND 2 (LED 2)

// Enable Pins
const int enable_9 = 9;     // Holds NAND 1 Input 2 HIGH

// ==================================================
// TIMER 1: For the Alternating Phases (Uses millis)
// ==================================================
unsigned long previousMillis = 0; 
const unsigned long phaseTime = 500;  // MANUALLY CHANGE THIS (500 = half second)
bool isPin8Active = true;             // Tracks whose turn it is

// ==================================================
// TIMER 2: For Software PWM / Intensity (Uses micros)
// ==================================================
unsigned long previousMicros = 0;
const unsigned long pwmPeriod = 5000; // 5000 microseconds = 200Hz Refresh Rate
bool pwmState = false;                // Tracks the fast flickering for dimming

void setup() {
  pinMode(pin8_Signal, OUTPUT);
  pinMode(pin7_Signal, OUTPUT);
  pinMode(enable_9, OUTPUT);  
  
  // Set the Enable pins HIGH so the NAND gates act as inverters
  digitalWrite(enable_9, HIGH);    
  
  // Start with both OFF (HIGH = OFF for inverted NAND)
  digitalWrite(pin8_Signal, LOW);
  digitalWrite(pin7_Signal, LOW);
}

void loop() {
  // ---------------------------------------------------------
  // 1. MACRO TIMER: Switch between Pin 8 and Pin 7
  // ---------------------------------------------------------
  unsigned long currentMillis = millis();
  if (currentMillis - previousMillis >= phaseTime) {
    previousMillis = currentMillis;       // Reset timer
    isPin8Active = !isPin8Active;         // Flip the active pin
  }

  // ---------------------------------------------------------
  // 2. READ POTENTIOMETER FOR INTENSITY ONLY
  // ---------------------------------------------------------
  int potValue = analogRead(potPin);
  
  // Map pot to how many microseconds the LED should be ON during the PWM cycle
  unsigned long onDuration = map(potValue, 0, 1023, 0, pwmPeriod); 

  // ---------------------------------------------------------
  // 3. MICRO TIMER: Generate the PWM signal without delays
  // ---------------------------------------------------------
  unsigned long currentMicros = micros();
  
  // If a full PWM period (5000us) has passed, start a new cycle
  if (currentMicros - previousMicros >= pwmPeriod) {
    previousMicros = currentMicros;
    pwmState = true;  // Start the cycle by turning LED ON
  }
  
  // If the ON time for this specific cycle has passed, turn it OFF
  if (currentMicros - previousMicros >= onDuration) {
    pwmState = false;
  }

  // ---------------------------------------------------------
  // 4. APPLY THE LOGIC TO THE PINS
  // ---------------------------------------------------------
  if (isPin8Active) {
    
    // It is Pin 8's turn. Pin 7 MUST remain strictly OFF.
    digitalWrite(pin7_Signal, HIGH); 
    
    // Apply the fast PWM state to Pin 8 (Remember: LOW = ON, HIGH = OFF)
    if (pwmState && onDuration > 0) {
      digitalWrite(pin8_Signal, LOW); 
    } else {
      digitalWrite(pin8_Signal, HIGH);
    }
    
  } else {
    
    // It is Pin 7's turn. Pin 8 MUST remain strictly OFF.
    digitalWrite(pin8_Signal, HIGH);
    
    // Apply the fast PWM state to Pin 7
    if (pwmState && onDuration > 0) {
      digitalWrite(pin7_Signal, LOW);
    } else {
      digitalWrite(pin7_Signal, HIGH);
    }
    
  }
}