.content { width: 1024px; height: 768px; line-height: 1.5; position: absolute; left: 0; top: 0; right: 0; bottom: 0; margin: auto; box-sizing: border-box; padding-left: 50px; padding-right: 50px; font-size: 24px; font-family: 'microsoft yahei'; overflow: hidden; }
.content .out { display: none; }
.section-header { text-align: center; }
.section-header > h1 { position: absolute; top: 50%; left: 0; right: 0; margin: -72px 0 0; font-size: 48px; }
.section-header > h2 { position: absolute; top: 50%; left: 0; right: 0; margin: 42px 0 0; font-size: 28px; color: #666; }

.only-header > h1 { font-size: 36px; margin: 1em 0; }
.only-header pre, .only-header code { background-color: #eee; font-family: "Lucida Console", Monaco, monospace; padding: .5em; white-space: pre-wrap; word-wrap: break-word; }
.only-header code { padding: .2em .4em; margin: 0 .1em; }