@Override
    protected void onDraw(Canvas canvas) {

      Paint paint = new Paint();
      paint.setColor(Color.RED);
      paint.setTextSize(40);

      /*
       * draw the background
       */
      canvas.drawBitmap(mPool, 0, 0, null);

      /*
       * compute the new position of our object, based on accelerometer
       * data and present time.
       */

      final ParticleSystem particleSystem = mParticleSystem;
      final long now = mSensorTimeStamp + (System.nanoTime() - mCpuTimeStamp);
      final float sx = mSensorX;
      final float sy = mSensorY;

      particleSystem.update(sx, sy, now);

      final float xc = mXOrigin;
      final float yc = mYOrigin;
      final float xs = mMetersToPixelsX;
      final float ys = mMetersToPixelsY;

      String scor = "score: " + score.toString();

      // canvas.rotate(90);
      canvas.drawText(scor, xc, yc, paint);

      int i = 0;
      for (Particle p : particleSystem.mBalls) {
        /*
         * We transform the canvas so that the coordinate system matches
         * the sensors coordinate system with the origin in the center
         * of the screen and the unit is the meter.
         */

        i++;
        final float x = xc + particleSystem.getPosX(i) * xs;
        final float y = yc - particleSystem.getPosY(i) * ys;
        canvas.drawBitmap(p.bitmap, x, y, null);
      }

      // and make sure to redraw asap
      invalidate();
    }
    @Override
    protected void onDraw(Canvas canvas) {

      /*
       * draw the background
       */

      // canvas.drawBitmap(mWood, 0, 0, null);

      /*
       * compute the new position of our object, based on accelerometer
       * data and present time.
       */

      final ParticleSystem particleSystem = mParticleSystem;
      final long now = mSensorTimeStamp + (System.nanoTime() - mCpuTimeStamp);
      final float sx = mSensorX;
      final float sy = mSensorY;

      particleSystem.update(sx, sy, now);

      final float xc = mXOrigin;
      final float yc = mYOrigin;
      final float xs = mMetersToPixelsX;
      final float ys = mMetersToPixelsY;
      final Bitmap bitmap = mBitmap;
      final int count = particleSystem.getParticleCount();
      for (int i = 0; i < count; i++) {
        /*
         * We transform the canvas so that the coordinate system matches
         * the sensors coordinate system with the origin in the center
         * of the screen and the unit is the meter.
         */

        final float x = xc + particleSystem.getPosX(i) * xs;
        final float y = yc - particleSystem.getPosY(i) * ys;
        canvas.drawBitmap(bitmap, x, y, mPaint);
      }

      // and make sure to redraw asap
      invalidate();
    }