#define interruptPin1 12
#define interruptPin2 14
int i=0;
int speed=400;
int LED[]={16,17,18,19};

void setup(){
for(i=0;i<4;i++){
pinMode(LED[i], OUTPUT);}
pinMode(interruptPin1, INPUT_PULLUP);
pinMode(interruptPin2, INPUT_PULLUP);

attachInterrupt(digitalPinToInterrupt(interruptPin1), increaseDelay, FALLING);
attachInterrupt(digitalPinToInterrupt(interruptPin2), decreaseDelay, FALLING);
Serial.begin(9600);
}

void loop(){
for(i=0;i<4;i++){
  digitalWrite(LED[i],HIGH);
  delay(speed);}
for(i=4;i>=0;i--){
  digitalWrite(LED[i],LOW);
  delay(speed);}
}

void increaseDelay(){
speed+=100;
Serial.print("LEDs run slower | ");
Serial.print("Delay = ");
Serial.println(speed);
delay(2000);
}

void decreaseDelay(){
speed-=100;
Serial.print("LEDs run faster | ");
Serial.print("Delay = ");
Serial.println(speed);
delay(2000);
}