#define led1 9
#define led2 10
#define led3 11

void setup() {
  
  pinMode(led1,OUTPUT);// put your setup code here, to run once:
 pinMode(led2,OUTPUT);
  pinMode(led3,OUTPUT);
}

void loop() {
  //light fading in - slowing turning on
  for(int i=0; i<=50;i++){
    analogWrite(led1,i);
        analogWrite(led2,i);
    analogWrite(led3,i);

    delay(40);
  }
  delay((500));
 // light fading out - slowly turning off
  for(int j=50; j>=0; j--){
    analogWrite(led1,j);
        analogWrite(led2,j);
    analogWrite(led3,j);

    delay(40);
  }
 delay((500));
}