Double box/border? Is this possible in CSS?

问题

I'm trying to recreate this image in CSS.

This is what I got from experimenting, so far. I used box-shadow to act as the second box. I'm not sure if there's a better way to do this?

h4 {
  font-family: sans-serif;
  text-transform: uppercase;
  text-align: center;
  border: solid 3px black;
  border-radius: 5px;
  text-decoration: none;
  font-weight: 600;
  color: black;
  letter-spacing: 2px;
  padding: 20px 15px;
  background: white;
  box-shadow: 10px 5px 0px 0px #ffffff, 11px 7px 0px 2px #000000;
}

<h4>3. Scouting for a location</h4>

回答1:

You can achieve this via absolutely position pseudo element. Also avoid property duplication via CSS inheritance.

.border {
  text-align: center;
  border: solid 3px black;
  border-radius: 5px;
  text-decoration: none;
  font-weight: 600;
  color: black;
  letter-spacing: 2px;
  padding: 20px 15px;
  margin: 15px 15px;
  background: white;
  
  position: relative; /* new */
}

/* new */
.border:after {
  content: "";
  position: absolute;
  display: block;
  background: inherit;
  border-radius: inherit;
  border: inherit;
  left: 2px;
  top: 2px;
  width: 100%;
  height: 100%;
  z-index: -1;
}

<div class="border">3. Scouting for a location</div>

回答2:

The concept behind using box-shadow is that two shadows, one white and one black, overlap to simulate a second black border. But the black shadow is only visible in the direction from which it is offset from the white shadow, so a gap is apparent between the original border and the black shadow (as shown in the OP's original post).

The "spread radius" of the black shadow could utilized to eliminate this gap (cleverly demonstrated by Nirav Joshi), but then the curvature of the corners is amplified and the two borders look different.

To duplicate the original border, I'd use ::after to generate an absolutely-positioned pseudo-element and use z-index to place it behind the original element. To further ensure that the border is duplicated exactly, I like Vadim Ovchinnikov's idea of inheriting the border color and radius from the original element.

.border {
  position: relative;
  text-align: center;
  border: solid 3px black;
  border-radius: 5px;
  text-decoration: none;
  font-weight: 600;
  color: black;
  letter-spacing: 2px;
  padding: 20px 15px;
  margin: 15px 15px;
  background: white;
}

.border::after {
  content: "";
  position: absolute;
  width: 100%;
  height: 100%;
  top: 3px;
  left: 3px;
  border: solid 3px black;
  border-radius: 5px;
  z-index: -1;
}

<h4 class="border">3. SCOUTING FOR A LOCATION</h4>

回答3:

Try this example

Hope it will help you.

.border {
text-align: center;
border: solid 3px black;
border-radius: 5px;
text-decoration: none;
font-weight: 600;
color: black;
letter-spacing: 2px;
padding: 20px 15px;
margin: 15px 15px;
background: white;
-webkit-box-shadow: 3px 3px 0px 0px #ffffff, 3px 3px 0px 3px #000000;
-moz-box-shadow: 3px 3px 0px 0px #ffffff, 3px 3px 0px 3px #000000;
box-shadow: 3px 3px 0px 0px #ffffff, 3px 3px 0px 3px #000000;
}