#define A_POS 27
#define A_NEG 14
#define B_POS 26
#define B_NEG 25

void setup() {
  pinMode(A_POS, OUTPUT);
  pinMode(A_NEG, OUTPUT);
  pinMode(B_POS, OUTPUT);
  pinMode(B_NEG, OUTPUT);
}

void loop() {
  // Step 1
  digitalWrite(A_POS,HIGH); digitalWrite(A_NEG,LOW);
  digitalWrite(B_POS,HIGH); digitalWrite(B_NEG,LOW);
  delay(200);

  // Step 2
  digitalWrite(A_POS,LOW); digitalWrite(A_NEG,HIGH);
  digitalWrite(B_POS,HIGH); digitalWrite(B_NEG,LOW);
  delay(200);

  // Step 3
  digitalWrite(A_POS,LOW); digitalWrite(A_NEG,HIGH);
  digitalWrite(B_POS,LOW); digitalWrite(B_NEG,HIGH);
  delay(200);

  // Step 4
  digitalWrite(A_POS,HIGH); digitalWrite(A_NEG,LOW);
  digitalWrite(B_POS,LOW); digitalWrite(B_NEG,HIGH);
  delay(200);
}