#define led 11
#define butt_up 8
#define butt_down 9

int brigthness = 0;
void setup() {
  pinMode(led, OUTPUT);
  pinMode(butt_up, INPUT_PULLUP);
  pinMode(butt_down, INPUT_PULLUP);
}
void loop() {
  if (digitalRead(butt_up) == 0) {
    brigthness = brigthness + 10;
  } else if (digitalRead(butt_down) == 0){
    brigthness = brigthness - 10;
  }

  if (brigthness > 255) {
    brigthness = 255;
  }
  if (brigthness < 0) {
    brigthness = 0;
  }

  analogWrite(led,brigthness);
}