HTML CSS LOGO of intridea. Not perfect, but yeah...

index.html

<p><span>i</span></p>

style.css

p {
  position: relative;
  width: 100px;
  height: 100px;
  margin: 100px;
  border: 15px solid green;
  border-radius: 5px 50px 30px 50px;
}

span {
  position: absolute;
  font-size: 120px;
  font-family: sans-serif;
  font-weight: bold;
  left: 38px;
  top:5px;
}
span:after {
  content: " ";
  width: 10px;
  height: 15px;
  box-shadow: 15px 15px white;
  position: absolute;
  top: 80px;
  left: 10px;
}
span:before {
  content: " ";
  width: 10px;
  height: 15px;
  box-shadow: 15px 15px white;
  position: absolute;
  top: 80px;

  left: -17px;
}