Point2d newCenter = snake_.getCenter();
Vector2d distanceDelta = new Vector2d( oldCenter_.x - newCenter.x, oldCenter_.y - newCenter.y );
velocity_ = distanceDelta.length() / (getNumStepsPerFrame() * timeStep_);
distance_.add( distanceDelta );
BackgroundGridRenderer bgRenderer = new BackgroundGridRenderer(gridColor_);
bgRenderer.drawGridBackground(g2, CELL_SIZE, XDIM, YDIM, distance_);
// draw the snake on the grid
snake_.translate( distanceDelta );
renderer.render(snake_, g2);