/*triangle background large*/
.triangle-bg-lg, .triangle-bg-lg:before, .triangle-bg-lg:after { width: 25em; height: 25em; }
/*triangle background medium*/
.triangle-bg-md, .triangle-bg-md:before, .triangle-bg-md:after { width: 20em; height: 20em; }
/*triangle background small*/
.triangle-bg-sm, .triangle-bg-sm:before, .triangle-bg-sm:after { width: 15em; height: 15em; }
/*triangle background extra small*/
.triangle-bg-xs, .triangle-bg-xs:before, .triangle-bg-xs:after { width: 10em; height: 10em; }
/*triangle background extra extra small*/
.triangle-bg-xxs, .triangle-bg-xxs:before, .triangle-bg-xxs:after { width: 5em; height: 5em; }
/*common triangle style*/
.triangle-bg-lg,.triangle-bg-md, .triangle-bg-sm,.triangle-bg-xs,.triangle-bg-xxs {
overflow: hidden;
position: relative;
margin:2em auto;
border-radius: 20%;
transform: translateY(50%) rotate(30deg) skewY(30deg) scaleX(.866);
}
.triangle-bg-lg:before, .triangle-bg-lg:after,.triangle-bg-md:before, .triangle-bg-md:after, .triangle-bg-sm:before, .triangle-bg-sm:after,.triangle-bg-xxs:before, .triangle-bg-xxs:after{
position: absolute;
background: #ccc;
pointer-events: auto;
content: '';
}
.triangle-bg-xs:before, .triangle-bg-xs:after{
background: #ccc;
position: absolute;
pointer-events: auto;
content: '';
}
.triangle-bg-lg:before, .triangle-bg-md:before, .triangle-bg-sm:before, .triangle-bg-xs:before,.triangle-bg-xxs:before {
border-radius: 20% 20% 20% 53%;
transform: scaleX(1.155) skewY(-30deg) rotate(-30deg) translateY(-42.3%)
skewX(30deg) scaleY(.866) translateX(-24%);
}
.triangle-bg-lg:after, .triangle-bg-md:after,.triangle-bg-sm:after,.triangle-bg-xs:after,.triangle-bg-xxs:after {
border-radius: 20% 20% 53% 20%;
transform: scaleX(1.155) skewY(-30deg) rotate(-30deg) translateY(-42.3%)
skewX(-30deg) scaleY(.866) translateX(24%);
}
<div class="page-container">
<div class="triangle-bg-lg"></div>
<div class="triangle-bg-md"></div>
<div class="triangle-bg-sm"></div>
<div class="triangle-bg-xs"></div>
<div class="triangle-bg-xxs"></div>
</div>