How to make a pure css triangle which has a white center

Question

I want to create an upward and downward facing arrow with css like the following: http://apps.eky.hk/css-triangle-generator/

However, instead of a solid color, I want to

Answer 1

Depending on how you're using it, you can make a triangle, with a border and even box shadow, without the triangle border hack, using CSS transform: rotate(). See my answer here: https://stackoverflow.com/a/8867645/918414

Answer 2

If you want to create a triangle with borders (or box shadow look-alike) in pure CSS, you should use pseudo-elements :before and :after.

In my example, I added display:inline-block; to the element .arrow-dropdown to be able to create some kind of dropdown menu with a drop shadow. It is followed by .arrow-only which is a a basic triangle with a red border.

body {
    margin: 10px;
    background: #1670c4;
}
.text {
    display: inline-block;
    font-size: 15px;
    color: #fff;
    text-shadow: 1px 1px 2px rgba(0,0,0,0.4);
    cursor: default;
}
.arrow-dropdown {
    display: inline-block;
    position: relative;
    vertical-align: middle;
    margin: 1px 0 0 8px;
    width: 8px;
    height: 7px;
}
.arrow-dropdown:after {
    content: '';
    position: absolute;
    border-style: solid;
    border-width: 7px 4px 0;
    border-color: #fff transparent transparent transparent;
    display: block;
    width: 0;
    z-index: 1;
}
.arrow-dropdown:before {
    content: '';
    position: absolute;
    border-style: solid;
    border-width: 8px 5px 0;
    border-color: rgba(0,0,0,0.3) transparent transparent transparent;
    display: block;
    width: 0;
    z-index: 0;
}
.arrow-only {
    position: relative;
    vertical-align: middle;
    margin: 10px 0 0 8px;
    width: 8px;
    height: 7px;
}
.arrow-only:after {
    content: '';
    position: absolute;
    border-style: solid;
    border-width: 12px 9px 0;
    border-color: #fff transparent transparent transparent;
    display: block;
    width: 0;
    z-index: 1;
}
.arrow-only:before {
    content: '';
    position: absolute;
    border-style: solid;
    border-width: 15px 11px 0;
    border-color: #f00 transparent transparent transparent;
    display: block;
    width: 0;
    z-index: 0;
    margin:-1px 0 0 -2px;
}

<div class="text">
  Dropdown text
</div><div class="arrow-dropdown"></div>

<div class="arrow-only"></div>

Answer 3

I think you could get a good idea of what to do by checking out this tutorial on pure css thought bubbles. It's doing what you're looking for.

http://www.sitepoint.com/pure-css3-speech-bubbles/

Answer 4

To create triangles with only CSS we use a zero width/height element with borders:

.arrow-up {
    width  : 0;
    height : 0;

    border-left   : 50px solid transparent;
    border-right  : 50px solid transparent;
    border-bottom : 50px solid black;
}

Since we are using borders to create the arrow, we can't just give it a border, but we can overlay one arrow on top of a slightly larger arrow to make the appearance of a border:

HTML --

<div class="top"></div>
<div class="bottom"></div>​

CSS --

.top {
    position : absolute;
    top      : 6px;
    left     : 10px;
    width    : 0;
    height   : 0;
    z-index  : 100;
    
    border-left   : 50px solid transparent;
    border-right  : 50px solid transparent;
    border-bottom : 50px solid black;
}
.bottom {
    position : absolute;
    width    : 0;
    height   : 0;
    z-index  : 99;
    
    border-left   : 60px solid transparent;
    border-right  : 60px solid transparent;
    border-bottom : 60px solid red;
}​

Here is a demo: http://jsfiddle.net/jasper/qnmpb/1/

Update

You can then put both of the triangle DIV elements inside a container and move that container however you want:

HTML --

<div id="container">
    <div class="top"></div>
    <div class="bottom"></div>
</div>

CSS --​

#container {
    position : relative;
    top      : 25px;
    left     : 25px;
}

Here is a demo: http://jsfiddle.net/jasper/qnmpb/3/

EDIT (2014):

I just came back to this answer and noticed that separate HTML elements are not necessary to create your double-triangle. You can use pseudo-elements, :before and :after. I.e. replace the .top selector with something like .my-element-that-needs-a-triangle:before and the .bottom selector with something like .my-element-that-needs-a-triangle:after.