style.css

/* TOC */

#TOC ul,
#TOC li,
#TOC span,
#TOC a {
  margin: 0;
  padding: 0;
  position: relative;
}
#TOC {
  line-height: 1;
  border-radius: 5px 5px 0 0;
  background: #141414;
  background: linear-gradient(to bottom, #333333 0%, #141414 100%);
  border-bottom: 2px solid #0fa1e0;
  position: fixed;
  z-index: 1;
  width: 90%;
}
#TOC:after,
#TOC ul:after {
  content: '';
  display: block;
  clear: both;
}
#TOC a {
  background: #141414;
  background: linear-gradient(to bottom, #333333 0%, #141414 100%);
  color: #ffffff;
  display: block;
  padding: 19px 20px;
  text-decoration: none;
  text-shadow: none;
}
#TOC ul {
  list-style: none;
}
#TOC > ul > li {
  display: inline-block;
  float: left;
  margin: 0;
}
#TOC > ul > li > a {
  color: #ffffff;
}
#TOC > ul > li:hover:after {
  content: '';
  display: block;
  width: 0;
  height: 0;
  position: absolute;
  left: 50%;
  bottom: 0;
  border-left: 10px solid transparent;
  border-right: 10px solid transparent;
  border-bottom: 10px solid #0fa1e0;
  margin-left: -10px;
}
#TOC > ul > li:first-child > a {
  border-radius: 5px 0 0 0;
}
#TOC.align-right > ul > li:first-child > a,
#TOC.align-center > ul > li:first-child > a {
  border-radius: 0;
}
#TOC.align-right > ul > li:last-child > a {
  border-radius: 0 5px 0 0;
}
#TOC > ul > li.active > a,
#TOC > ul > li:hover > a {
  color: #ffffff;
  box-shadow: inset 0 0 3px #000000;
  background: #070707;
  background: linear-gradient(to bottom, #262626 0%, #070707 100%);
}
#TOC .has-sub {
  z-index: 1;
}
#TOC .has-sub:hover > ul {
  display: block;
}
#TOC .has-sub ul {
  display: none;
  position: absolute;
  width: 300px;
  top: 100%;
  left: 0;
}
#TOC .has-sub ul li a {
  background: #0fa1e0;
  border-bottom: 1px dotted #31b7f1;
  filter: none;
  display: block;
  line-height: 120%;
  padding: 10px;
  color: #ffffff;
}
#TOC .has-sub ul li:hover a {
  background: #0c7fb0;
}
#TOC ul ul li:hover > a {
  color: #ffffff;
}
#TOC .has-sub .has-sub:hover > ul {
  display: block;
}
#TOC .has-sub .has-sub ul {
  display: none;
  position: absolute;
  left: 100%;
  top: 0;
}
#TOC .has-sub .has-sub ul li a {
  background: #0c7fb0;
  border-bottom: 1px dotted #31b7f1;
}
#TOC .has-sub .has-sub ul li a:hover {
  background: #0a6d98;
}
#TOC ul ul li.last > a,
#TOC ul ul li:last-child > a,
#TOC ul ul ul li.last > a,
#TOC ul ul ul li:last-child > a,
#TOC .has-sub ul li:last-child > a,
#TOC .has-sub ul li.last > a {
  border-bottom: 0;
}
#TOC ul {
  font-size: 1.2rem;
}

/* CUSTOM BLOCKS */

.rmd-caution {
  padding: 1em 1em 1em 4em;
  margin-bottom: 10px;
  background: /* #FFFF99 */ url("images/1459472920_attention.png") left center/3em no-repeat !important;
  border-style:solid;
  border-color:#FFFF00;
}
.rmd-caution:before {
  font-style: italic;
  content: "";
}
.rmd-details {
  padding: 1em 1em 1em 4em;
  margin-bottom: 10px;
  background: /* #99FF99 */ url("images/1459472947_idea.png") left center/3em no-repeat !important;
  border-style:solid;
  border-color:#00FF00;
}
.rmd-details:before {
  font-style: italic;
  content: "";
}

/* EXTRA BOOK TITLE SPACING */

.level1 {
  margin-top: 60px;
}

/* TOC FORMATTING TWEAKS */
/*
  set spacing so that links go to the right place

  (considering the floating top bar's height)
*/

.section::before {
  /*Using @Jerry's answer http://stackoverflow.com/a/9618795/ */
  content:"";
  display:block;
  height:60px;
  margin:-60px 0 0;
}

/* 
  ensure floating TOC doesn't display when printing

  as far as i can tell, this does not work (to hide TOC when printing) 
  it should be used in conjunction with the include arg to html_book, 
  but that arg breaks violently, so...
*/

@media print {
  #TOC, TOC {
    display: none;
  }
}

/* 
  shrink blockquote text size vs rmarkdown default
  italicize and color so it still stands out
*/

blockquote {
  background: #f5f5f0;
  font-size: medium;
  font-style: italic;
}