Inverted Scooped corners using CSS

Answer 1

You can create a concaved radius using the box-shadow property.

1. This technique creates a transparant square with overflow hidden.

2. It then creates a transparant circle with a box shadow.

3. We then adjust the position of the circle to only view 1 quarter of it.

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SNIPPET

#box {
  position: relative;
  width: 200px;
  height: 50px;
  background-color: blue;
  border-radius: 9999px 0 0 9999px;
  margin: 30px;
  text-align: center;
  color: #fff;
  padding-top: 10px;
}

#top,
#bottom {
  position: absolute;
  height: 30px;
  width: 30px;
  right: 0;
  overflow: hidden;
}

#top {
  top: -30px;
}

#bottom {
  bottom: -30px;
}

#top::before,
#bottom::before {
  content: '';
  position: absolute;
  right: 0;
  height: 200%;
  width: 200%;
  border-radius: 100%;
  box-shadow: 10px 10px 5px 100px blue;
  z-index: -1;
}

#top::before {
  top: -100%;
}

  

  #box