const int ledPin = 9;

const int button1 = 2;
const int button2 = 3;
const int button3 = 4;

int brightness1 = 85;   // ~33% (PWM: 0–255)
int brightness2 = 170;  // ~66%
int brightness3 = 255;  // 100%

void setup() {
  pinMode(ledPin, OUTPUT);

  pinMode(button1, INPUT_PULLUP);
  pinMode(button2, INPUT_PULLUP);
  pinMode(button3, INPUT_PULLUP);
}

void loop() {
  if (digitalRead(button1) == LOW) {
    analogWrite(ledPin, brightness1);
  } else if (digitalRead(button2) == LOW) {
    analogWrite(ledPin, brightness2);
  } else if (digitalRead(button3) == LOW) {
    analogWrite(ledPin, brightness3);
  }
}