<div class="wrapper">
  <div class="textarea">
    <p>congratulations!</p>
    <div class="tri right-triangle"></div>
    <div class="tri left-triangle"></div>
    <div class="excess-right"></div>
    <div class="excess-left"></div>
    <div class="tri top-right"></div>
    <div class="tri top-left"></div>
    <div class="tri bottom-right"></div>
    <div class="tri bottom-left"></div>
   </div> 
</div>

body {
  background: #37C5DB;
}
.wrapper {
  padding:50px;
}
.textarea {
  background: #fff;
  color: black;
  width: 70%;
  display: block;
  height: 100px;
  position: relative;
  /* z-index: 1000; */
  margin: 0 auto;
  border-bottom-left-radius: 3px;
  border-bottom-right-radius: 3px;
}
.textarea p {
  padding: 30px;
  text-align: center;
  z-index: 101;
  font-family: Helvetica;
  font-size: 30px;
}
.tri {
  width: 0;
  height: 0;
  border-style: solid;
  position: absolute;
}
.left-triangle {
  border-width: 30px 0 0 70px;
  border-color: transparent transparent transparent #555;
  top: -30px;
  right: 0px;
  z-index: 99;
}
.right-triangle {
  border-width: 0 0 30px 70px;
  border-color: transparent transparent #555 transparent;
  top: -30px;
  left: 0px;
  z-index: 99;
}
.excess-right {
  height: 100px;
  width: 100px;
  background: black;
  position: absolute;
  top: -33px;
  right: -30px;
  z-index: -100;
  border-top-left-radius: 3px
}
.excess-left {
  height: 100px;
  width: 100px;
  background: black;
  position: absolute;
  top: -33px;
  left: -30px;
  z-index: -100;
  border-top-right-radius: 3px;
}
.top-right {
border-width: 49px 50px 0 0;
border-color: black transparent transparent transparent;
  top: -33px;
  right: -80px;
}
.bottom-right {
  border-width: 49px 0 0 50px;
border-color: transparent transparent transparent black;
  top: 18px;
  right: -80px;
}
.top-left {
  border-width: 0 50px 49px 0;
border-color: transparent black transparent transparent;
top: -33px;
  left: -80px;
}
.bottom-left {
  top: 18px;
  left: -80px;
  border-width: 0 0 49px 50px;
border-color: transparent transparent black transparent;

}