function solution_hide()
{
    $link = document.getElementById('solution_link');
    $link.innerHTML = '<p>To view the solution for the puzzle, <a href="javascript:solution_show()">click here</a>.</p>';

    $solution = document.getElementById('sudoku_solution');
    $solution.style.visibility = "hidden";
}

function solution_show()
{
    $link = document.getElementById('solution_link');
    $link.innerHTML = '<p>Solution <a href="javascript:solution_hide()">(hide)</a></p>';
    $solution = document.getElementById('sudoku_solution');
    $solution.style.visibility = "visible";
}