/*Write a program to interface LEDs at any 
two PWM pins and button, to exhibit LED
fading at the click of button*/
int led1=10;
int led2=11;
int led3=12;
int led4=13;
int incr=7;
int decr=8;
int led_counter=0;
void setup() {
  pinMode(led1, OUTPUT);
  pinMode(led2, OUTPUT);
  pinMode(led3, OUTPUT);
  pinMode(led4, OUTPUT);
  pinMode(incr, INPUT);
  pinMode(decr, INPUT);
}

void loop() {
  if(digitalRead(incr))
  {
    led_counter++;
    }
  if(digitalRead(decr))
  {
    led_counter--;
    }
switch(led_counter)
{
  case 0:
  digitalWrite(led1, LOW);
  digitalWrite(led2, LOW);
  digitalWrite(led3, LOW);
  digitalWrite(led4, LOW);
  break;
  case 1:
  digitalWrite(led1, HIGH);
  digitalWrite(led2, LOW);
  digitalWrite(led3, LOW);
  digitalWrite(led4, LOW);
  break;
  case 2:
  digitalWrite(led1, HIGH);
  digitalWrite(led2, HIGH);
  digitalWrite(led3, LOW);
  digitalWrite(led4, LOW);
  break;
  case 3:
  digitalWrite(led1, HIGH);
  digitalWrite(led2, HIGH);
  digitalWrite(led3, HIGH);
  digitalWrite(led4, LOW);
  break;
  case 4:
  digitalWrite(led1, HIGH);
  digitalWrite(led2, HIGH);
  digitalWrite(led3, HIGH);
  digitalWrite(led4, HIGH);
  break;
}
  delay(500);

}