如何创建一些常见的CSS3不规则形状

.triangle {
  width: 0;
  height: 0;
  border-top: 50px solid #007bff;
  border-left: 50px solid transparent;
}

.trapezoid {
  height: 0;
  width: 100px;
  border-top: 50px solid #007bff;
  border-bottom: 50px solid #007bff;
  border-left: 25px solid transparent;
  border-right: 25px solid transparent;
}

.parallelogram {
  width: 150px;
  height: 100px;
  transfORM: skew(20deg);
  background-color: #007bff;
}

.ellipse {
  width: 100px;
  height: 50px;
  border-radius: 50%;
  background-color: #007bff;
}

.star {
  height: 0;
  width: 0;
  border-right: 50px solid transparent;
  border-bottom: 50px solid #007bff;
  border-left: 50px solid transparent;
  transform: rotate(35deg);
}

.star:before {
  height: 0;
  width: 0;
  margin: -50px 0 0 -25px;
  content: "";
  position: absolute;
  border-right: 25px solid transparent;
  border-bottom: 30px solid #fff;
  border-left: 25px solid transparent;
  transform: rotate(-35deg);
}

.star:after {
  width: 0;
  height: 0;
  margin: -20px 0 0 -10px;
  content: "";
  position: absolute;
  border-right: 10px solid transparent;
  border-bottom: 12px solid #007bff;
  border-left: 10px solid transparent;
  transform: rotate(35deg);
}