function show_play_page(){
window.open("play.php", "NPuzzle", "width=1000px, height=800px, toolbar = 0, location = 0, directories = 0,");
}
function show_login_page(){
document.location = "login.php";
}
function show_register_page(){
document.location = "register.php";
}
function go_home(){
document.location = "index.html";
}