// variable
//push buttons
char green_pb = 27;
char blue_pb = 25;
//LEDs
char red_led = 23;
char green_led = 18;

void setup() {
  Serial.begin(115200);
  pinMode(green_pb, INPUT);
  pinMode(blue_pb, INPUT);
  pinMode(red_led, OUTPUT);
  pinMode(green_led, OUTPUT);
  digitalWrite(red_led, HIGH);
  digitalWrite(green_led, HIGH);
}

void loop() {
  // reading push buttons
  //0: pressed; 1: released
  char green_pb_val;
  char blue_pb_val;

  green_pb_val = digitalRead(green_pb);
  blue_pb_val = digitalRead(blue_pb);

  // Case 1: both pressed->both on
  if( (green_pb_val == 0) && (blue_pb_val == 0) )
  {
   digitalWrite(green_led, LOW);
   digitalWrite(red_led, LOW);
  }

  // Case 2: only green pb -> turn on green only
  if( (green_pb_val == 0) && (blue_pb_val == 1) )
  {
   digitalWrite(green_led, LOW);
   digitalWrite(red_led, HIGH);
  }

  // Case 3: only blue pb -> turn on red only
  if( (green_pb_val == 1) && (blue_pb_val == 0) )
  {
   digitalWrite(green_led, HIGH);
   digitalWrite(red_led, LOW);
  }

  // Case 4: no pressing -> turn off both
  if( (green_pb_val == 1) && (blue_pb_val == 1) )
  {
   digitalWrite(green_led, HIGH);
   digitalWrite(red_led, HIGH);
  }
}