* otherwise.
     */
    public boolean onScreen(Tile tileToCheck) {
        if (tileToCheck == null)
            return false;
        repositionMapIfNeeded();
        return tileToCheck.getY() - 2 > topRow
            && tileToCheck.getY() + 4 < bottomRow
            && tileToCheck.getX() - 1 > leftColumn
            && tileToCheck.getX() + 2 < rightColumn;
    }