Creating a triangle with CSS only

Question

I am developing a responsive web application and I need to create two separate content areas as follows:

So far I tried

border-right: 30px solid transparent;
border-bottom: 30px solid #4c4c4c; 
height: 100%;
width: 100%;
position: fixed;

But, unfortunately, it was not possible to create a triangle.

Is there any other way to create a triangle using CSS with the ability to fully contact the contents inside the div using the border property?

Any help would be greatly appreciated.

Answer 1

I believe that you are looking for triangles with borders and a transparent slice between them (which, apparently, none of the existing answers apply to), and here is an example. This is absolutely possible, but requires a lot of hacking.

CSS Transforms:

. , , , ..

.container {
  position: relative;
  overflow: hidden;
  height: 200px;
  width: 200px;
}
.div-1,
.div-2 {
  position: absolute;
  top: 0px;
  left: 0px;
  height: 100%;
  width: 100%;
  overflow: hidden;
}
.div-1 {
  top: calc(-100% - 5px);
  transform: skewY(45deg);
  transform-origin: left top;
  border-bottom: 2px solid;
}
.div-1:after {
  position: absolute;
  content: '';
  height: calc(100% - 2px);
  width: calc(100% - 2px);
  top: calc(100% + 7px);
  left: 0px;
  transform: skewY(-45deg);
  transform-origin: left top;
  border: 1px solid;
}
.div-2 {
  top: 5px;
  transform: skewY(45deg);
  transform-origin: left bottom;
  border-top: 1px solid;
}
.div-2:after {
  position: absolute;
  content: '';
  height: calc(100% - 7px);
  width: calc(100% - 7px);
  top: 0px;
  left: 0px;
  transform: skewY(-45deg);
  transform-origin: left bottom;
  border: 1px solid;
}
* {
  box-sizing: border-box;
}

/* just for demo */
.container{
  transition: all 1s;
}
.container:hover{
  width: 400px;
  height: 400px;
}
body{
  background: radial-gradient(circle at center, aliceblue, mediumslateblue);
  min-height: 100vh;
}

<script src="https://cdnjs.cloudflare.com/ajax/libs/prefixfree/1.0.7/prefixfree.min.js"></script>
<div class='container'>
  <div class='div-1'></div>
  <div class='div-2'></div>
</div>

Hide result

---

:

, . . (1) . (2) Angular , . (3) 2 div , , , , .

.container {
  position: relative;
  overflow: hidden;
  height: 200px;
  width: 300px;
  background: linear-gradient(to top right, transparent calc(50% + 2px), black calc(50% + 2px), black calc(50% + 4px), transparent calc(50% + 4px)), linear-gradient(to bottom left, transparent calc(50% + 2px), black calc(50% + 2px), black calc(50% + 4px), transparent calc(50% + 4px)) ;
    }
.container:before{
  position: absolute;
  content: '';
  height: calc(100% - 6px);
  width: calc(100% - 6px);
  left: 4px;
  border-top: 2px solid black;
  border-right: 2px solid black;
}
.container:after{
  position: absolute;
  content: '';
  height: calc(100% - 6px);
  width: calc(100% - 6px);
  top: 4px;
  border-left: 2px solid black;
  border-bottom: 2px solid black;
}
/* just for demo */
.container{
  transition: all 1s;
}
.container:hover{
  width: 700px;
  height: 400px;
}
body{
  background: radial-gradient(circle at center, aliceblue, mediumslateblue);
  min-height: 100vh;
}

<script src="https://cdnjs.cloudflare.com/ajax/libs/prefixfree/1.0.7/prefixfree.min.js"></script>
<div class='container'>
</div>

Hide result

---

SVG:

, SVG . , path, .

.container {
  position: relative;
  height: 300px;
  width: 200px;
}
svg {
  position: absolute;
  top: 0px;
  left: 0px;
  height: 100%;
  width: 100%;
}
svg path {
  fill: transparent;
  stroke: black;
}
/* just for demo */

.container {
  transition: all 1s;
}
.container:hover {
  height: 400px;
  width: 700px;
}
body {
  background: radial-gradient(circle at center, aliceblue, mediumslateblue);
  min-height: 100vh;
}

<script src="https://cdnjs.cloudflare.com/ajax/libs/prefixfree/1.0.7/prefixfree.min.js"></script>
<div class='container'>
  <svg viewBox='0 0 100 100' preserveAspectRatio='none'>
    <path d='M4,2 L98,2 98,96 4,2z M2,4 L2,98 96,98 2,4z' vector-effect='non-scaling-stroke' />
  </svg>
</div>

Hide result

.. ( ) . , , CSS Shapes shape-inside .

Answer 2

.

.triangle1 {
    border-right: 30px solid transparent;
   border-bottom: 30px solid #4c4c4c; 
   position: fixed;
}

.

.triangle1 {
    border-right: 100px solid transparent;
    border-bottom: 100px solid #4c4c4c; 
    position: fixed;
}
.triangle2 {
    border-left: 100px solid transparent;
    border-top: 100px solid #4c4c4c; 
    position: fixed;
    margin-left: 3px;
}

<div class="triangle1">
</div>

<div class="triangle2">
</div>

Hide result

Edit:

.

div .

Fiddle

Answer 3

.triangle1 {
    width: 0; 
    height: 0; 
    border-left: 0px solid transparent;
    border-right: 200px solid transparent;
    border-bottom: 150px solid black;
}

DIV 1. .

Answer 4

HTML:

<div id="DIV-Element1"></div>
<div id="DIV-Element2"></div>

Css:

#DIV-Element1 { width: 0; height: 0; border-bottom: 100px solid black; border-right: 100px solid transparent; }
#DIV-Element2 { width: 0; height: 0; margin-left: 15px;border-top: 100px solid black; border-left: 100px solid transparent; }

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