#include "Keyboard.h" // library Keyboard.h

#define PIN_LED 15 //Declare LED on pin 15
#define PIN_BTN_1 5 //Declare BTN UP on pin 5
#define PIN_BTN_2 8 //Declare BTN LEFT on pin 8
#define PIN_BTN_3 14 // Declare BTN DOWN on pin 14
#define PIN_BTN_4 4 // Declare BTN RIGHT on pin 4
#define PIN_BTN_5 31 // Declare BTN SPACEBAR on pin 31

#define N_BTN 5 // Declare Num BTN


int pin_btns[] = {PIN_BTN_1, PIN_BTN_2, PIN_BTN_3, PIN_BTN_4, PIN_BTN_5}; //ARRAY OF PIN_BTN
byte key_btns[] = {KEY_UP_ARROW,KEY_LEFT_ARROW,KEY_DOWN_ARROW,KEY_RIGHT_ARROW,' '}; //declare function of buttons
int state_btns[] = {false,false,false,false,false}; //Button status creation in the down position
int state_btns_new[] = {false,false,false,false,false}; //Creation of a 2nd state of the buttons in the down position for comparison

void setup() {
  pinMode(PIN_LED, OUTPUT);
  
  for (int i=0; i < N_BTN; i++) {
    pinMode(pin_btns[i], INPUT_PULLUP);
  }
  Keyboard.begin();
  SerialUSB.begin(0);
  
}

void loop() {
  int val; //Creation of a "val" to insert the number of the activated button
  bool state; //Creation of "state" with boolean type 0/1
  bool led=false; //Creation of a boolean value to set the led to false
  for (int i = 0; i < N_BTN; i++) {
    val = digitalRead(pin_btns[i]); //In 'val' we will put read the position of the engaged button
    state_btns_new[i] = !val;The inverse of 'val' is assigned in 'state_btns_new'.
  }
  
  for (int i = 0; i < N_BTN; i++) {
    if (state_btns_new[i] && !state_btns[i]){ 
        Keyboard.press(key_btns[i]);
    }
    if (!state_btns_new[i] && state_btns[i]){
      Keyboard.release(key_btns[i]);
    }

    led |= state_btns_new[i]; //if true LED ON else OFF 

    state_btns[i] = state_btns_new[i];
  }
  digitalWrite(PIN_LED, led);
  delay(1); 
}