const int led1 = 0;
void setup() {
  pinMode(led1, OUTPUT);

}
int delayTime = 1000;

void loop() {
  delayTime = delayTime - 100;

  if(delayTime <= 0){
    delayTime = 1000;
  }
  digitalWrite(led1, HIGH);
  delay(delayTime);
  digitalWrite(led1, LOW);
  delay(delayTime);
}