 #define MOTOR_FORWARD_TURN          33
 #define MOTOR_REVERSE_FULL          44
 #define MOTOR_REVERSE_TURN          55
+#define MOTOR_RAMP_STEP             5
 
 #define BUTTON_MASK                 0x10
 #define JOYSTICK_MASK               0x0F

          digitalWrite(front_motor_b[i], LOW);
          digitalWrite(rear_motor_a[i], HIGH);
          digitalWrite(rear_motor_b[i], LOW);
          analogWrite(front_motor_en[i], FULL_SPEED);
          analogWrite(rear_motor_en[i], FULL_SPEED);
        break;

        case MOTOR_FORWARD_TURN:

          digitalWrite(rear_motor_b[i], HIGH);
          analogWrite(front_motor_en[i], TURN_SPEED);
          analogWrite(rear_motor_en[i], TURN_SPEED);
          motor_drive_target[i] = TURN_SPEED;
        break;

        default:
