.left {
  float: left;
}

.right {
  float: right;
}

.clear::after {
  content: "";
  display: block;
  clear: both;
}

.w1200 {
  width: 1200px;
  margin: 0 auto;
}

@media (max-width:1200px) {

  .w1200 {
    width: 992px;
  }
}

@media (max-width:992px) {

  .w1200 {
    width: 768px;
  }
}

@media (max-width:768px) {

  .w1200 {
    width: 90%;
  }
}


/* 小节标题 */
.section-title {
  width: 100%;
  margin: 0 auto;
  padding: 40px 0;

  text-align: center;
  letter-spacing: .1em;
}

.section-title .title {
  font-size: 30px;
  font-weight: bold;
}

.section-title .desc {
  font-size: 14px;
}

/* 倒三角 */

.triangle::after {
  display: block;
  content: '';
  width: 0;
  height: 0;
  border-left: 8px solid transparent;
  border-right: 8px solid transparent;
  border-top: 10px solid #fff;
}