How to create a corset like effect with CSS?

Question

I want to create a effect as below with CSS, initially, I was thinking to merge two rectangle with rounded corner, but I can\'t use that way since it is a sharp angle, not round

Answer 1

In my opinion you would either have to work with borders (as you did) or SVGs. For the shadow it does not work with borders and regular css-shadows, so you want to apply drop-shadow as a filter (or you can use a SVG for the shadow).

This is what I came up with

.triangle_left {
  width: 600px;
  height: 600px;
  position: relative;
  margin: 20px auto;
  border: 2px solid #cccccc;
  /* box-shadow: 0px 0px 8px 1px darkgrey; */
  border-radius: 20px;
}

.triangle_left:before {
  content: '';
  width: 0;
  height: 0;
  border-top: 30px solid transparent;
  border-left: 30px solid white;
  border-bottom: 30px solid transparent;
  filter: drop-shadow(4px 0px 0px #ccc);
  position: absolute;
  left: -6px;
  top: 50%;
}

.triangle_left:after {
  content: '';
  width: 0;
  height: 0;
  border-top: 30px solid transparent;
  border-right: 30px solid white;
  border-bottom: 30px solid transparent;
  filter: drop-shadow(-4px 0px 0px #ccc);
  position: absolute;
  right: -6px;
  top: 50%;
}