.m-chapter-list {
  position: relative;
  margin-top: 20px;
  margin-left: 20px;
  border-top: 1px solid #f8f8f8;
}
.m-chapter-list a {
  width: 100%;
  height: 45px;
  border-bottom: 1px solid #f8f8f8;
  font-size: 16px;
  display: block;
  box-sizing: border-box;
  padding-left: 6px;
  position: relative;
}
.m-chapter-list .current {
  border-left: 5px solid #3290d4;
  background-color: #fff;
}
.m-chapter-list .current a {
  color: #3290d4;
  width: 400px;
  background-color: #fff;
  border-right: 2px solid #fff;
}

.m-chapter-list .current .sub-list {
  display: block;
}
.m-chapter-list .current .sub-list a {
  color: #666;
  font-size: 14px;
  line-height: 30px;
}
.m-chapter-list .current .sub-list a:before {
  content: "";
  border: 1px solid;
  width: 8px;
  border-color: transparent transparent #ddd #ddd;
  display: inline-block;
  margin-right: 5px;
  position: relative;
  top: -3px;
}
.m-chapter-list .current .sub-list a:hover,
.m-chapter-list .current .sub-list a.current {
  color: #3290d4;
  border-left: 0;
}
.m-chapter-list .sub-list {
  display: none;
}