const int RED_PIN = 9;
const int GREEN_PIN = 10;
const int BLUE_PIN = 11;

int DELAY = 200;

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

void loop() {
  displayAllBasicColors();
  showSpectrum();
}

void displayAllBasicColors() {
  // RED light
  digitalWrite(RED_PIN, HIGH);
  digitalWrite(GREEN_PIN, LOW);
  digitalWrite(BLUE_PIN, LOW);

  delay(DELAY);

  // YELLOW light
  digitalWrite(RED_PIN, HIGH);
  digitalWrite(GREEN_PIN, HIGH);
  digitalWrite(BLUE_PIN, LOW);

  delay(DELAY);

  // GREEN light
  digitalWrite(RED_PIN, LOW);
  digitalWrite(GREEN_PIN, HIGH);
  digitalWrite(BLUE_PIN, HIGH);
  delay(DELAY);
}

void showRGB(int color) {
  int redPWM;
  int greenPWM;
  int bluePWM;

  if (color <= 255) {
    redPWM = 255 - color; // red from on -> off
    greenPWM = color; // green from off -> on
    bluePWM = 0; // blue always off
  }
  else if (color <= 511) {
    redPWM = 0; // red always off
    greenPWM = 255 - (color - 256); //gren from on -> off
    bluePWM = (color - 256); //blue from off -> on
  }
  else {
    redPWM = (color - 512); // red from off-> on
    greenPWM = 0; //green always off
    bluePWM = 255 - (color - 512); // blue from on->off
  }

  analogWrite(RED_PIN, redPWM);
  analogWrite(GREEN_PIN, greenPWM);
  analogWrite(BLUE_PIN, bluePWM);
}

void showSpectrum() {
  for (int i=0; i < 768; i++) {
    showRGB(i);
    delay(10);
  }
}