int LED_pin1=11;
int LED_pin2=10;
int LED_pin3=9;
int LED_pin4=8;

void setup() {
   pinMode(11, OUTPUT);
   pinMode(10, OUTPUT);
   pinMode(9, OUTPUT);
   pinMode(8, OUTPUT);
}

void loop() {
  int value=analogRead(A0);
  int brightness=map(value,0,1023,0,255);
  if(brightness>0&&brightness<100){
  digitalWrite(11, HIGH);
  digitalWrite(10, LOW);
  digitalWrite(9, LOW);
  digitalWrite(8, LOW);
  }
  else if(brightness>100&&brightness<170){
  digitalWrite(11, HIGH);
  digitalWrite(10, HIGH);
  digitalWrite(9, LOW);
  digitalWrite(8, LOW);
  }
  else if(brightness>170&&brightness<210){
  digitalWrite(11, HIGH);
  digitalWrite(10, HIGH);
  digitalWrite(9, HIGH);
  digitalWrite(8, LOW);
  }
  else if(brightness>210&&brightness<255){
  digitalWrite(11, HIGH);
  digitalWrite(10, HIGH);
  digitalWrite(9, HIGH);
  digitalWrite(8, HIGH);
  }
  delay(20);
}