var home_up = 'home_up.png';
var home_over = 'home_over.png';
var home_disabled = 'home_disabled.png';

var exit_up = 'exit_up.png';
var exit_over = 'exit_over.png';
var exit_disabled = 'exit_disabled.png';

var glossary_up = 'glossary_up.png';
var glossary_over = 'glossary_over.png';
var glossary_disabled = 'glossary_disabled.png';

var mute_up = 'mute_up.png';
var mute_over = 'mute_over.png';
var mute_disabled = 'mute_disabled.png';

var next_up = 'next_up.png';
var next_over = 'next_over.png';
var next_disabled = 'next_disabled.png';

var previous_up = 'previous_up.png';
var previous_over = 'previous_over.png';
var previous_disabled = 'previous_disabled.png';

var coursemap_up = 'coursemap_up.png';
var coursemap_over = 'coursemap_over.png';
var coursemap_disabled = 'coursemap_disabled.png';

var replay_up = 'replay_up.png';
var replay_over = 'replay_over.png';
var replay_disabled = 'replay_disabled.png';

var search_up = 'search_up.png';
var search_over = 'search_over.png';
var search_disabled = 'search_disabled.png';

var help_up = 'help_up.png';
var help_over = 'help_over.png';
var help_disabled = 'help_disabled.png';

var print_up = 'print_up.png';
var print_over = 'print_over.png';
var print_disabled = 'print_disabled.png';

var guide_up = 'guide_up.png';
var guide_over = 'guide_over.png';
var guide_disabled = 'guide_disabled.png';

var faq_up = 'faq_up.png';
var faq_over = 'faq_over.png';
var faq_disabled = 'faq_disabled.png';

var resources_up = 'resources_up.png';
var resources_over = 'resources_over.png';
var resources_disabled = 'resources_disabled.png';