#define RED_PIN 3   // PWM pin for Red LED
#define GREEN_PIN 6 // PWM pin for Green LED
#define BLUE_PIN  10  // PWM pin for Blue LED
#define FADE_SPEED 10 // lower is faster

// Gamma table for brightness correction
const uint8_t PROGMEM gamma8[] = {
  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,
  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  1,  1,  1,  1,
  1,  1,  1,  1,  1,  1,  1,  1,  1,  2,  2,  2,  2,  2,  2,  2,
  2,  3,  3,  3,  3,  3,  3,  3,  4,  4,  4,  4,  4,  5,  5,  5,
  5,  6,  6,  6,  6,  7,  7,  7,  7,  8,  8,  8,  9,  9,  9, 10,
  10, 10, 11, 11, 11, 12, 12, 13, 13, 13, 14, 14, 15, 15, 16, 16,
  17, 17, 18, 18, 19, 19, 20, 20, 21, 21, 22, 22, 23, 24, 24, 25,
  25, 26, 27, 27, 28, 29, 29, 30, 31, 32, 32, 33, 34, 35, 35, 36,
  37, 38, 39, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 50,
  51, 52, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 66, 67, 68,
  69, 70, 72, 73, 74, 75, 77, 78, 79, 81, 82, 83, 85, 86, 87, 89,
  90, 92, 93, 95, 96, 98, 99, 101, 102, 104, 105, 107, 109, 110, 112, 114,
  115, 117, 119, 120, 122, 124, 126, 127, 129, 131, 133, 135, 137, 138, 140, 142,
  144, 146, 148, 150, 152, 154, 156, 158, 160, 162, 164, 167, 169, 171, 173, 175,
  177, 180, 182, 184, 186, 189, 191, 193, 196, 198, 200, 203, 205, 208, 210, 213,
  215, 218, 220, 223, 225, 228, 231, 233, 236, 239, 241, 244, 247, 249, 252, 255
};

void setup() {
  pinMode(RED_PIN, OUTPUT);
  pinMode(GREEN_PIN, OUTPUT);
  pinMode(BLUE_PIN, OUTPUT);
}

void loop() {
  // Fade between Red, Green, and Blue LEDs
  for (int i = 0; i < 255; i++) {
    analogWrite(RED_PIN, pgm_read_byte(&gamma8[i]));  // Fade in Red
    analogWrite(GREEN_PIN, 0);                       // Green off
    analogWrite(BLUE_PIN, 0);                        // Blue off
    delay(FADE_SPEED);
  }
  for (int i = 255; i > 0; i--) {
    analogWrite(RED_PIN, pgm_read_byte(&gamma8[i]));  // Fade out Red
    delay(FADE_SPEED);
  }

  for (int i = 0; i < 255; i++) {
    analogWrite(GREEN_PIN, pgm_read_byte(&gamma8[i]));  // Fade in Green
    analogWrite(RED_PIN, 0);                           // Red off
    analogWrite(BLUE_PIN, 0);                          // Blue off
    delay(FADE_SPEED);
  }
  for (int i = 255; i > 0; i--) {
    analogWrite(GREEN_PIN, pgm_read_byte(&gamma8[i]));  // Fade out Green
    delay(FADE_SPEED);
  }

  for (int i = 0; i < 255; i++) {
    analogWrite(BLUE_PIN, pgm_read_byte(&gamma8[i]));   // Fade in Blue
    analogWrite(RED_PIN, 0);                           // Red off
    analogWrite(GREEN_PIN, 0);                         // Green off
    delay(FADE_SPEED);
  }
  for (int i = 255; i > 0; i--) {
    analogWrite(BLUE_PIN, pgm_read_byte(&gamma8[i]));   // Fade out Blue
    delay(FADE_SPEED);
  }
}