ADXL 335 as mouse cursor

I am working on a project which i am going to use the arduino leonardo board and the ADXL 335 accelerometer to make a mouse.

I want to use the ADXL 335 to control the movement of the cursor. However, there is something wrong happened.

const int switchPin = 2;      // switch to turn on and off mouse control
const int mouseButton = 0;    // input pin for the mouse pushButton
const int xAxis = A1;         // joystick X axis  
const int yAxis = A2;         // joystick Y axis
int fsrReading;

// parameters for reading the joystick:
int range = 12;               // output range of X or Y movement
int responseDelay = 5;        // response delay of the mouse, in ms
int threshold = range/4;      // resting threshold
int center = range/2;         // resting position value

boolean mouseIsActive = true;    // whether or not to control the mouse
int lastSwitchState = LOW;        // previous switch state

void setup() {
  pinMode(mouseButton, INPUT);
 // take control of the mouse:

void loop() {
  // read and scale the two axes:
  int xReading = readAxis(A1);
  int yReading = readAxis(A2);

  // if the mouse control state is active, move the mouse:
  if (mouseIsActive) {
    Mouse.move(xReading, yReading, 0);

   int clickState = analogRead(mouseButton);
   // if the mouse button is pressed:
   if (clickState > 0) {
    // if the mouse is not pressed, press it:
    if (!Mouse.isPressed(MOUSE_LEFT)) {; 
  // else the mouse button is not pressed:
  else {
    // if the mouse is pressed, release it:
    if (Mouse.isPressed(MOUSE_LEFT)) {

int readAxis(int thisAxis) { 
  // read the analog input:
  int reading = analogRead(thisAxis);

  reading = map(reading, 0, 1023, 0, range);

  int distance = reading - center;
  return distance;

The above code are modified from the arduino examples. ( mouse button control and the joysticks mouse control )
For the mouse button control, I have already done it and there is no problem.

But for the mouse cursor control, after running the program, I found that the cursor keeps moving upwards.
Can someone point out where is the problem?