How to make 3-corner-rounded triangle in CSS

Question

I'd like to achieve a custom-colored shape like this using no Javascript:

Currently I'm overlaying an image of the 'frame' over an orange rectangular div, but this is pretty hacky. I suppose I could use a dynamically generated canvas element, but that not only requires JS, but HTML5 canvas support. Any ideas?

Answer 1

My best attempt: http://dabblet.com/gist/4592062

Pixel perfection at any size, uses simpler math than Ana's original solution, and is more intuitive in my opinion :)

.triangle {
	position: relative;
	background-color: orange;
	text-align: left;
}
.triangle:before,
.triangle:after {
	content: '';
	position: absolute;
	background-color: inherit;
}
.triangle,
.triangle:before,
.triangle:after {
	width:  10em;
	height: 10em;
	border-top-right-radius: 30%;
}

.triangle {
	transform: rotate(-60deg) skewX(-30deg) scale(1,.866);
}
.triangle:before {
	transform: rotate(-135deg) skewX(-45deg) scale(1.414,.707) translate(0,-50%);
}
.triangle:after {
	transform: rotate(135deg) skewY(-45deg) scale(.707,1.414) translate(50%);
}

<div class="triangle"></div>