如何制作装饰元素（见图）

html,
body {
  position: relative;
  background-color: #308a56;
  color: #fff;
  font-size: 20px;
  line-height: 20px;
}

.item {
  position: relative;
  padding: 3rem;
  text-align: center;
}

.item+.item {
  margin-top: -2px;
}

.item:after {
  content: '';
  position: absolute;
  display: block;
  bottom: -2px;
  border-bottom: 2px dashed #fff;
  left: 6.6rem;
  right: 6.6rem;
}

.item__text {
  height: 1rem
}

.item__num {
  position: absolute;
  border: 2px solid #fff;
  line-height: 3rem;
  font-size: 1rem;
  top: 2rem;
  height: 3rem;
  width: 3rem;
  border-radius: 3rem;
  background-color: #308a56;
  z-index: 2;
}

.item_left .item__num {
  left: 1rem
}

.item_right .item__num {
  right: 1rem
}

.item_center .item__num {
  right: 0;
  left: 0;
  margin: auto;
}

.item__num:after {
  content: '';
  position: absolute;
  display: block;
  bottom: -2rem;
  border-bottom: 2px dashed #fff;
  height: 2rem;
  width: 4rem;
  z-index: 1
}

.item_left .item__num:after {
  left: 50%;
  border-left: 2px dashed #fff;
  border-radius: 100% / 0 0 0 3rem;
}

.item_right .item__num:after {
  right: 50%;
  border-right: 2px dashed #fff;
  border-radius: 100% / 0 0 3rem 0;
}

.item__num:before {
  content: '';
  position: absolute;
  display: block;
  top: -2rem;
  border-top: 2px dashed #fff;
  height: 2rem;
  width: 4rem;
  z-index: 1;
}

.item_left .item__num:before,
.item_center .item__num:before {
  left: 50%;
  border-left: 2px dashed #fff;
  border-radius: 100% / 3rem 0 0 0;
}

.item_right .item__num:before {
  right: 50%;
  border-right: 2px dashed #fff;
  border-radius: 100% / 0 3rem 0 0;
}

.items .item:first-child .item__num:before,
.items .item:last-child .item__num:after,
.items .item:last-child:after {
  display: none;
}
.item.item_before-center:after {
  left: calc(4rem + 50%)
}

<div class="items">
  <div class="item item_left">
    <div class="item__num">1</div>
    <div class="item__text">text</div>
  </div>
  <div class="item item_right">
    <div class="item__num">2</div>
    <div class="item__text">text</div>
  </div>
  <div class="item item_left">
    <div class="item__num">3</div>
    <div class="item__text">text</div>
  </div>
  <div class="item item_before-center item_right">
    <div class="item__num">4</div>
    <div class="item__text">text</div>
  </div>
  <div class="item item_center">
    <div class="item__num">⌄</div>
  </div>
</div>