const byte led = 9;
byte x, y = 0;

void setup() {
  // put your setup code here, to run once:

}

void loop() {
  // put your main code here, to run repeatedly:

if (y == 0) {
x = x + 1;
analogWrite(led, x);
delay(10);
}
 if (x == 255) {
y = y - 225;
analogWrite(led, y);
delay(10);
 }

}