#include <Bounce2.h>

#define led1pin 11 
#define led2pin 10 
#define led3pin 9 
#define led4pin 6 

#define drukknop1 13     
#define drukknop2 12

Bounce debounceddrukknop1 = Bounce();  
Bounce debounceddrukknop2 = Bounce();  

int counter = 0;  // Startwaarde

void setup() {
  pinMode(led1pin, OUTPUT);
  pinMode(led2pin, OUTPUT);
  pinMode(led3pin, OUTPUT);
  pinMode(led4pin, OUTPUT);
  pinMode(drukknop1, INPUT);  
  pinMode(drukknop2, INPUT);

  debounceddrukknop1.attach(drukknop1);
  debounceddrukknop1.interval(50); 

  debounceddrukknop2.attach(drukknop2);
  debounceddrukknop2.interval(50); 
}

void loop() {
  debounceddrukknop1.update();
  debounceddrukknop2.update();

  if (debounceddrukknop1.fell()) {
    counter++;
  }
  if (debounceddrukknop2.fell()) { 
    counter--;
  }

  if (counter > 4) {  
    counter = 4;
  }

  switch (counter) {
    case 0:
      digitalWrite(led1pin, LOW);
      digitalWrite(led2pin, LOW);
      digitalWrite(led3pin, LOW);
      digitalWrite(led4pin, LOW);
      break;
    case 1:
      digitalWrite(led1pin, HIGH);
      digitalWrite(led2pin, LOW);
      digitalWrite(led3pin, LOW);
      digitalWrite(led4pin, LOW);
      break;
    case 2:
      digitalWrite(led1pin, HIGH);
      digitalWrite(led2pin, HIGH);
      digitalWrite(led3pin, LOW);
      digitalWrite(led4pin, LOW);
      break;
    case 3:
      digitalWrite(led1pin, HIGH);
      digitalWrite(led2pin, HIGH);
      digitalWrite(led3pin, HIGH);
      digitalWrite(led4pin, LOW);
      break;
    case 4:
      digitalWrite(led1pin, HIGH);
      digitalWrite(led2pin, HIGH);
      digitalWrite(led3pin, HIGH);
      digitalWrite(led4pin, HIGH);
      break;
  
    default:
      digitalWrite(led1pin, HIGH);
      digitalWrite(led2pin, HIGH);
      digitalWrite(led3pin, HIGH);
      digitalWrite(led4pin, HIGH);
  }
}