span.cloze span.original {
    display: none;
}

span.cloze:hover span.clozed {
    display: none !important;
}

span.cloze:hover span.original { 
    display: inline !important; 
}

pre {
    white-space: pre-wrap;
    /* css-3 */
    white-space: -moz-pre-wrap;
    /* Mozilla, since 1999 */
    white-space: -pre-wrap;
    /* Opera 4-6 */
    white-space: -o-pre-wrap;
    /* Opera 7 */
    word-wrap: break-word;
    /* Internet Explorer 5.5+ */
}

.hidden {
    display:none;
}

.section-marker {
    font-weight: bold; /* Or any other style you want */
}