const int kPinButton1 = 2;
const int kPinButton2 = 3;
const int kPinLed = 9;

void setup() {
  // put your setup code here, to run once:
  pinMode(kPinButton1, INPUT);
  pinMode(kPinButton2, INPUT);
  pinMode(kPinLed, OUTPUT);
  digitalWrite(kPinButton1, HIGH);
  digitalWrite(kPinButton2, HIGH);
}
int ledBrightness = 128;

void loop() {
  // put your main code here, to run repeatedly:
  if (digitalRead(kPinButton1) == LOW){
    ledBrightness--;
  }
  else if (digitalRead(kPinButton2)==LOW){
    ledBrightness++;
  }
  ledBrightness = constrain(ledBrightness, 0, 255);
  analogWrite(kPinLed, ledBrightness);
  delay(20);
}