Exam

#define LED_PIN 13
int DT = 2000;

void setup() {
 pinMode(LED_PIN,OUTPUT);
 Serial.begin(9600);
 Serial.println("Please select: \n + - increase_speed \n - - decrease_speed");
}

void loop() {
 
  char inp;
 
  if(Serial.available() > 0){
   inp = Serial.read();
   if (inp == '+') {
     DT = DT + 200;
   }
     else if (inp == '-'){
     DT = DT+ - 200;
   } else{
     DT = 2000;
   }
 }
 digitalWrite(LED_PIN, HIGH);
 delay(DT);
 digitalWrite(LED_PIN, LOW);
 delay(DT);

}