带边框的方形 div。只显示角点[重复]

我有一个在我的网站上使用的播放器。
我想更改播放按钮的外观。

我想用虚线边框来做到这一点，然后增加破折号之间的空间。那行不通。

我无法使用图像。有没有CSS(3)解决方案？

我希望它看起来像这样。

这真的都是关于角落的！

- - - - - - - 更新 - - - - - - - -

所以我使用了@Naila的解决方案来使其工作。 运行遇到以下问题：

I use Video.js插件WordPress我正在创建一个新皮肤

当我正在关注css我发现已经有一个::before-pseudo 处理播放箭头。

The ::before-伪箭头表示宽度为 100%，这有助于箭头位于中心。 因为我使用30%的宽度来使边框成为一个角。这会覆盖之前的 100% 宽度。结果如下：

这里是：
CodePen

如果你刚刚在 CSS 字段中跳过这个 CSS，你就会到达我现在所在的位置并看到问题：

/*
Player Skin Designer for Video.js
http://videojs.com

To customize the player skin edit 
the CSS below. Click "details" 
below to add comments or questions.
This file uses some SCSS. Learn more  
at http://sass-lang.com/guide)

This designer can be linked to at:
http://codepen.io/heff/pen/EarCt/left/?editors=010
*/

// The following are SCSS variables to automate some of the values.
// But don't feel limited by them. Change/replace whatever you want. 

// The color of icons, text, and the big play button border.
// Try changing to #0f0
$primary-foreground-color: #fff; // #fff default
// The default color of control backgrounds is mostly black but with a little
// bit of blue so it can still be seen on all-black video frames, which are c ommon.
// Try changing to #900
$primary-background-color: #2B333F;  // #2B333F default

// Try changing to true
$center-big-play-button: true; // true default

.video-js {
 /* The base font size controls the size of everything, not just text.
 All dimensions use em-based sizes so that the scale along with the font size.
 Try increasing it to 15px and see what happens. */
 font-size: 10px;

 /* The main font color changes the ICON COLORS as well as the text */
 color: $primary-foreground-color;
}

/* The "Big Play Button" is the play button that shows before the video plays.
To center it set the align values to center and middle. The typical location
of the button is the center, but there is trend towards moving it to a corner
where it gets out of the way of valuable content in the poster image.*/
.vjs-default-skin .vjs-big-play-button {
  /* The font size is what makes the big play button...big. 
 All width/height values use ems, which are a multiple of the font size.
 If the .video-js font-size is 10px, then 3em equals 30px.*/
 font-size: 3em;

 /* We're using SCSS vars here because the values are used in multiple places.
 Now that font size is set, the following em values will be a multiple of the
 new font size. If the font-size is 3em (30px), then setting any of
 the following values to 3em would equal 30px. 3 * font-size. */
 $big-play-width: 3em; 
  /* 1.5em = 45px default */
  $big-play-height: 3em;

 line-height: $big-play-height;
 height: $big-play-height;
 width: $big-play-width;

 /* 0.06666em = 2px default */
 /* 0.3em = 9px default */
 border:none;
 border-radius:0;

 @if $center-big-play-button {
 /* Align center */
left: 50%;
top: 50%;
margin-left: -($big-play-width / 2);
margin-top: -($big-play-height / 2);   
} @else {
/* Align top left. 0.5em = 15px default */
left: 0.5em;
top: 0.5em;
}
}
.vjs-big-play-button:before {
 position: absolute;
content: "";
width: 30px !important;
height: 30px!important;
right: -2px;
bottom: -2px;
 border-left: 2px solid $primary-foreground-color;
border-top: 2px solid $primary-foreground-color;
}
.vjs-big-play-button:after {
 position: absolute;
 content: "";
 width: 30px;
 height: 30px;
 right: -2px;
 bottom: -2px;
 border-right: 2px solid $primary-foreground-color;
 border-bottom: 2px solid $primary-foreground-color;
}

/* The default color of control backgrounds is mostly black but with a little
  bit of blue so it can still be seen on all-black video frames, which are     common. */
.video-js .vjs-control-bar,
.video-js .vjs-big-play-button,
.video-js .vjs-menu-button .vjs-menu-content {
  /* IE8 - has no alpha support */
  background-color: $primary-background-color;
  /* Opacity: 1.0 = 100%, 0.0 = 0% */
  background-color: rgba($primary-background-color, 0.7);
}

// Make a slightly lighter version of the main background
// for the slider background.
$slider-bg-color: lighten($primary-background-color, 33%);

/* Slider - used for Volume bar and Progress bar */
.video-js .vjs-slider {
 background-color: $slider-bg-color;
 background-color: rgba($slider-bg-color, 0.5);
}

/* The slider bar color is used for the progress bar and the volume bar
(the first two can be removed after a fix that's coming) */
.video-js .vjs-volume-level,
.video-js .vjs-play-progress,
.video-js .vjs-slider-bar {
background: $primary-foreground-color;
}

/* The main progress bar also has a bar that shows how much has been loaded.     */
.video-js .vjs-load-progress {
  /* For IE8 we'll lighten the color */
  background: lighten($slider-bg-color, 25%);
  /* Otherwise we'll rely on stacked opacities */
  background: rgba($slider-bg-color, 0.5);
}

/* The load progress bar also has internal divs that represent
 smaller disconnected loaded time ranges */
.video-js .vjs-load-progress div {
  /* For IE8 we'll lighten the color */
  background: lighten($slider-bg-color, 50%);
  /* Otherwise we'll rely on stacked opacities */
  background: rgba($slider-bg-color, 0.75);
}

我们可以这样做pseudo元素，查看演示

.box {
  width: 200px;
  height: 200px;
  margin: 15px auto;
  background: #999;
  position: relative;
}
.box:before {
  position: absolute;
  content: "";
  width: 30px;
  height: 30px;
  top: -2px;
  left: -2px;
  z-index:-1;
  border-left: 2px solid red;
  border-top: 2px solid red;
}
.box:after {
  position: absolute;
  content: "";
  width: 30px;
  height: 30px;
  right: -2px;
  bottom: -2px;
  z-index:-1;
  border-right: 2px solid red;
  border-bottom: 2px solid red;
}

<div class="box"></div>