float RGB[3];
int ldrPin = 4;     // LDR in Analog Input 0 to read the ambient light
int ambientLight;   // variable to store the value of the ambient light
int redLed   = 9;  // red LED in Digital Pin 11 (PWM)
int greenLed = 5;  // green LED in Digital Pin 10 (PWM)
int blueLed  = 7;   // blue LED in Digital Pin 9 (PWM)

void setup(){
  pinMode(redLed,OUTPUT);  // tell arduino it's an output
  pinMode(greenLed,OUTPUT);// tell arduino it's an output
  pinMode(blueLed,OUTPUT); // tell arduino it's an output

  // set all the outputs to low
  digitalWrite(redLed,LOW);
  digitalWrite(greenLed,LOW);
  digitalWrite(blueLed,LOW);
}

void loop(){
  for (float x=0;x<PI;x=x+0.00001){
    RGB[0]=255*abs(sin(x*(180/PI)));           // calculate the brightness for the red led
    RGB[1]=255*abs(sin((x+PI/3)*(180/PI)));    // calculate the brightness for the green led
    RGB[2]=255*abs(sin((x+(2*PI)/3)*(180/PI)));// calculate the brightness for the blue led
    ambientLight=analogRead(ldrPin); // read an store the ambient light
    if(ambientLight<600){ // start only if the ambient light is very low
      //  write the brightness on the leds
      analogWrite(redLed,RGB[0]);
      analogWrite(greenLed,RGB[1]);
      analogWrite(blueLed,RGB[2]);
    }
    else{
      digitalWrite(redLed,LOW);
      digitalWrite(greenLed,LOW);
      digitalWrite(blueLed,LOW);
    }
    for(int i=0;i<3;i++){
      if(RGB[i]<1){
        delay(100);
      }
      if(RGB[i]<5){
        delay(50);
      }
      if(RGB[i]<10){
        delay(10);
      }
      if(RGB[i]<100){
        delay(5);
      }
    }
    delay(1);
  }
}