border - Rounded trapezoid with CSS

Question

I'm having a slight problem with css. I need a trapezoid div which upper left corner(the one with the angle above 90 degrees) is rounded. I already know that this:

HTML:

<div style="margin:30px">
  <div class="trapezoid">
  </div>
</div>

CSS:

.trapezoid{
  vertical-align: middle;
  border-bottom: 31px solid red;
  border-left: 25px solid transparent;
  height: 0;
  width: 150px;
}

produces a trapezoid. I tried the border-top-left-radius property, however the effect is not sufficent enough.

Here's a jsfiddle with the above code to, well, fiddle with: http://jsfiddle.net/n3TLP/5/

I there is more info needed just comment.
Thanks in advance :)

Answer 1

Not that you should ever do this, but you can also create a rounded corner trapezoid with a single element by applying CSS 3d transformations:

.trapezoid {
  position: relative;
  width: 300px;
  height: 200px;
  overflow: hidden;
}

.trapezoid:after {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  width: 200%;
  height: 100%;
  background: red;
  border-radius: 20px 0 0 0;
  -webkit-transform-origin: 100% 100%;
  -moz-transform-origin: 100% 100%;
  -ms-transform-origin: 100% 100%;
  -o-transform-origin: 100% 100%;
  transform-origin: 100% 100%;
  -webkit-transform: perspective(400px) rotateX(45deg);
  -moz-transform:  perspective(400px) rotateX(45deg);
  -ms-transform: perspective(400px) rotateX(45deg);
  -o-transform: perspective(400px) rotateX(45deg);
  transform: perspective(400px) rotateX(45deg);
}

?

http://jsfiddle.net/RzJTP/