const int potPin = A0;      
const int stepPin = 2;      
const int dirPin = 3;      

void setup() {
  pinMode(stepPin, OUTPUT);
  pinMode(dirPin, OUTPUT);
  pinMode(potPin, INPUT);
}

void loop() {
  int potValue = analogRead(potPin);         // Read potentiometer value
  int delayTime = map(potValue, 0, 1023, 300, 2000);  // Map to delay time

  digitalWrite(dirPin, HIGH);               // Set rotation direction

  digitalWrite(stepPin, HIGH);
  delayMicroseconds(delayTime);
  digitalWrite(stepPin, LOW);
  delayMicroseconds(delayTime);
}