int potpin = 0;  // analog pin used to connect the potentiometer
int val;    // variable to read the value from the analog pin

void setup() {

    pinMode(9, OUTPUT);

}

void loop() {
  val = analogRead(potpin);            // reads the value of the potentiometer (value between 0 and 1023)
  
  val = map(val, 0, 1023, 0, 255);     // scale it to use it with the light (value between 0 and 255)
  
  analogWrite(9, val);                  // sets the LED brightness according to the scaled value
  

}