@Override
public void mouseMoved(MouseEvent e) {
SetGameViewer viewer = (SetGameViewer)viewer_;
SetGameRenderer renderer = (SetGameRenderer)viewer.getBoardRenderer();
Card card =
renderer.findCardOver(viewer.getBoard(), e.getX(), e.getY(),
viewer.getWidth(), viewer.getHeight());
boolean changed = card != currentlyHighlightedCard_;
if (changed) {