// Define Pins & Delay
#define BLUE 4
#define GREEN 5
#define RED 6
#define DELAY 10

// define global variables
int redValue;
int greenValue;
int blueValue;
int redDir = -1;
int greenDir = 1;
int blueDir = 0;


void setup() {
  pinMode(RED, OUTPUT);
  pinMode(GREEN, OUTPUT);
  pinMode(BLUE, OUTPUT);
  
  redValue = 0;
  greenValue = 0;
  blueValue = 255;

  analogWrite(RED, redValue);
  analogWrite(GREEN, greenValue);
  analogWrite(BLUE, blueValue);

  Serial.begin(9600);
  
}



// main loop
void loop() {
  if (redValue == 255) {
    redDir = -1;
    greenDir = 1;
    blueDir = 0;
  } else if (greenValue == 255) {
    redDir = 0;
    greenDir = -1;
    blueDir = 1;
  } else if (blueValue == 255) {
    redDir = 1;
    greenDir = 0;
    blueDir = -1;
  }

  redValue += redDir;
  greenValue += greenDir;
  blueValue += blueDir;

  analogWrite(RED, redValue);
  analogWrite(GREEN, greenValue);
  analogWrite(BLUE, blueValue);

  delay(DELAY);
}