css实现带圆角三角型的示例代码

<i class="triangle triangle-up"></i>
<i class="triangle triangle-right"></i>
<i class="triangle triangle-down"></i>
<i class="triangle triangle-left"></i>

.triangle{
  display: inline-block;
  font-size: 0;
  overflow: hidden;
}

.triangle:before{
  content: "";
  position: relative;
  display: inline-block;
  border: 25px solid transparent;
}

.triangle-up{
  position: relative;
  top: 2px;
  border-top-left-radius: 50%;
  border-top-right-radius: 50%;
}
.triangle-up:before{
  bottom: 2px;
  border-top-width: 0;
  border-bottom-width: 50px;
  border-bottom-color: rgb(181, 181, 181);
}

.triangle-right{
  position: relative;
  right: 2px;
  border-top-right-radius: 50%;
  border-bottom-right-radius: 50%;
}
.triangle-right:before{
  left: 2px;
  border-right-width: 0;
  border-left-width: 50px;
  border-left-color: rgb(181, 181, 181);
}

.triangle-down{
  position: relative;
  bottom: 2px;
  border-bottom-right-radius: 50%;
  border-bottom-left-radius: 50%;
}
.triangle-down:before{
  top: 2px;
  border-bottom-width: 0;
  border-top-width: 50px;
  border-top-color: rgb(181, 181, 181);
}

.triangle-left{
  position: relative;
  left: 2px;
  border-top-left-radius: 50%;
  border-bottom-left-radius: 50%;
}
.triangle-left:before{
  right: 2px;
  border-left-width: 0;
  border-right-width: 50px;
  border-right-color: rgba(181, 181, 181, 1);
}

<div class="bubble-box">
  <div class="bubble-box-hat">
    <i class="triangle triangle-up"></i>
  </div> 
  <div class="bubble-box-body">i am isaac!</div>
</div>

.bubble-box{
  font-size: 0;
  margin-top: 50px;
}

.bubble-box-hat{
  text-align: center;
}

.bubble-box-body{
  color: #FFFFFF;
  background: rgb(181, 181, 181);
  font-size: 28px;
  border-radius: 10px;
  padding: 100px;
  text-align: center;
}