Quarter of a ring with CSS and HTML

Problem

I'm trying to create a ring shape in css, divided into 4 quarters. Each quarter will represent a button.

I've been playing around with the following code:

#quarterCircleTopLeft{
     width:100px;
     height:100px;
     border:1px solid #000;
     background: orange;
     border-radius: 90px 0 70px 0;
     -moz-border-radius: 90px 0 70px 0;
     -webkit-border-radius: 90px 0 70px 0;
}

Which produces this (disregard the grey lines):

enter image description here

Obviously, I want the border at the right bottom to be inverted. However, since this is a button I cannot use another shape to produce a cutout (as this would overlap with other buttons of the menu). I've added a red line to show approx how I would want the border to go. Sorry, my paint skills are bad :-P

How can I invert the border or in another way produce the shape I want?

Problem courtesy of: Mythio

Solution

I'd do something like:

http://dabblet.com/gist/5476973

In short, lots of border radius + a white circle on top of everything.

On my example, I'd then bind click events onto the divs using javascript, or just make them all <a> elements instead and add a display:block;.

/**
* Quarter Circles
*/

.main {
  position: relative;
  width: 200px;
  height: 200px;
  margin: 0 auto;
}
.quarter {
  position: absolute;
  width: 50%;
  height: 50%;
  transition: background-color 0.2s ease-in-out;
}
.quarter:hover {
  background-color: pink;
}
.quarter1 {
  top: 0;
  left: 0;
  background-color: red;
  border-radius: 100% 0 0 0;
}
.quarter2 {
  top: 0;
  right: 0;
  background-color: blue;
  border-radius: 0 100% 0 0;
}
.quarter3 {
  bottom: 0;
  left: 0;
  background-color: orange;
  border-radius: 0 0 0 100%;
}
.quarter4 {
  bottom: 0;
  right: 0;
  background-color: green;
  border-radius: 0 0 100% 0;
}
.cutout {
  width: 50%;
  height: 50%;
  background-color: white;
  position: absolute;
  top: 25%;
  left: 25%;
  border-radius: 50%;
  pointer-events: none;
}
<div class="main">
  <div class="quarter quarter1"></div>
  <div class="quarter quarter2"></div>
  <div class="quarter quarter3"></div>
  <div class="quarter quarter4"></div>
  <div class="cutout"></div>
</div>

Solution courtesy of: Rich Bradshaw

Discussion

Here is an <svg> solution.

Svg has its own <a> element svg.
Just press the corners and you will find some amazing documentation ;)
Jokes aside The a link works on the shape so the shape gets the link.
This leaves the space empty space inside the shape that will show any thing behind it.

<svg width="150px" height="150px" viewbox="-1 -1 102 102">
  <a xlink:href="https://developer.mozilla.org/en-US/docs/SVG">
    <path stroke="tomato" fill="orange" d="M10 50 0 50 C 0 16 16 0 50 0 V0 20 
                                         C 31 20 20 31 20 50Z" />
  </a>
  <a xlink:href="https://developer.mozilla.org/en-US/docs/SVG">
    <path stroke="darkRed" fill="red" transform="translate(100, 0) rotate(90)" d="M10 50 0 50 C 0 16 16 0 50 0 V0 20 
                                         C 31 20 20 31 20 50Z" />
  </a>
  <a xlink:href="https://developer.mozilla.org/en-US/docs/SVG">
    <path stroke="DarkBlue" fill="blue" transform="translate(100, 100) rotate(180)" d="M10 50 0 50 C 0 16 16 0 50 0 V0 20 
                                         C 31 20 20 31 20 50Z" />
  </a>
  <a xlink:href="https://developer.mozilla.org/en-US/docs/SVG">
    <path stroke="darkGreen" href="#" fill="green" transform="translate(0, 100) rotate(-90)" d="M10 50 0 50 C 0 16 16 0 50 0 V0 20 
                                         C 31 20 20 31 20 50Z" />
  </a>
</svg>

Discussion courtesy of: Persijn

i have been able to enhance the 1st answer and avoid getting the ring respond when mouse is on cutoff area.

http://codepen.io/a-zaki/pen/rLRyAm

/**
* Quarter Circles
*/

.main {
  position: relative;
  width: 300px;
  height: 300px;
  margin: 0 auto;
}
.quarter {
  position: absolute;
  width: 50%;
  height: 50%;
  transition: background-color 0.2s ease-in-out;
  z-index: 1;
}
.quarter:hover {
  background-color: pink;
}
.quarter1 {
  top: 0;
  left: 0;
  background-color: red;
  border-radius: 100% 0 0 0;
}
.quarter2 {
  top: 0;
  right: 0;
  background-color: blue;
  border-radius: 0 100% 0 0;
}
.quarter3 {
  bottom: 0;
  left: 0;
  background-color: orange;
  border-radius: 0 0 0 100%;
}
.quarter4 {
  bottom: 0;
  right: 0;
  background-color: green;
  border-radius: 0 0 100% 0;
}
.cutout {
  width: 50%;
  height: 50%;
  background-color: white;
  position: absolute;
  top: 25%;
  left: 25%;
  border-radius: 50%;
  border: 3px solid #000;
  z-index: 2;
}
<div class="main">
  <div class="quarter quarter1"></div>
  <div class="quarter quarter2"></div>
  <div class="quarter quarter3"></div>
  <div class="quarter quarter4"></div>
  <div class="cutout"></div>
</div>

Discussion courtesy of: azaki

This recipe can be found in it's original form on Stack Over Flow.