int pinLED1 = 7;
int pinLED2 = 8;
int pinLED3 = 9;
int pinLED4 = 10;
int pinButton1 = 3;
int pinButton2= 4;
int short_delay = 500;

void setup() {
  pinMode(pinLED1, OUTPUT);
  pinMode(pinLED2, OUTPUT);
  pinMode(pinLED3, OUTPUT);
  pinMode(pinLED4, OUTPUT);
  pinMode(pinButton1, INPUT_PULLUP);
  pinMode(pinButton2, INPUT_PULLUP);
} 

void loop() {
 //local variable
  bool button1_state = digitalRead(pinButton1);
  bool button2_state = digitalRead(pinButton2);
  if (button1_state == HIGH && button2_state LOW) { // > < >= <= == |= Logical Operator: && ||
   digitalWrite(pinLED1, HIGH);
   delay(short_delay);
   digitalWrite(pinLED2, HIGH);
   delay(short_delay);
   digitalWrite(pinLED3, HIGH);
   delay(short_delay);
   digitalWrite(pinLED4, HIGH);
   delay(short_delay);

   digitalWrite(pinLED1, LOW);
   digitalWrite(pinLED2, LOW);
   digitalWrite(pinLED3, LOW);
   digitalWrite(pinLED4, LOW);
   delay(short_delay);
   }
  else if(button1_state == LOW && button2_state HIGH) {
  
   digitalWrite(pinLED1, HIGH);
   delay(short_delay);
   digitalWrite(pinLED2, LOW);
   delay(short_delay);
   digitalWrite(pinLED3, HIGH);
   delay(short_delay);
   digitalWrite(pinLED4, LOW);
   delay(short_delay);

   digitalWrite(pinLED1, LOW);
   digitalWrite(pinLED2, HIGH);
   digitalWrite(pinLED3, LOW);
   digitalWrite(pinLED4, HIGH);
   delay(short_delay);
 }
 else if (button1_state == HIGH && button2_state LOW){
  digitalWrite(pinLED1, HIGH);
   delay(short_delay);
   digitalWrite(pinLED2, LOW);
   delay(short_delay);
   digitalWrite(pinLED3, HIGH);
   delay(short_delay);
   digitalWrite(pinLED4, LOW);
   delay(short_delay);

   digitalWrite(pinLED1, LOW);
   digitalWrite(pinLED2, HIGH);
   digitalWrite(pinLED3, LOW);
   digitalWrite(pinLED4, HIGH);
   delay(short_delay);
 }
 else {
   digitalWrite(pinLED1, LOW);
   digitalWrite(pinLED2, LOW);
   digitalWrite(pinLED3, LOW);
   digitalWrite(pinLED4, LOW);
   delay(short_delay);
 } 
}