文本和下划线之间的差距

Question

我想知道为什么padding-bottom或margin-bottom不能用于下划线？在li中> a：在我添加padding-bottom之前它并没有创建任何类型的空间。我没有想法，你能帮助我吗？

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ul {
    list-style-type: none;
    margin: 0;
    padding: 0;
	  text-align: right;
	  line-height: 10vh;
	  margin-right: 10vh;
	  animation: fadein 5s;
    -moz-animation: fadein 5s; /* Firefox */
    -webkit-animation: fadein 5s; /* Safari and Chrome */
    -o-animation: fadein 5s; /* Opera */
    font-family: verdana;
}

li {
    display: inline;
    margin-left: 2.5vh;
	  margin-right: 5vh;
	  text-transform: uppercase;
}

a {
	  text-decoration:none;
	  color: white;
}

li > a {
	  position: relative;
  	color: black;
  	text-decoration: none;
}

li > a:hover {
    color: black;
}

li > a:before {
    content: "";
    position: absolute;
    width: 100%;
    height: 2px;
    padding-bottom: 3px;
    bottom: 0;
    left: 0;
    background-color: black;
    visibility: hidden;
    -webkit-transform: scaleX(0);
    transform: scaleX(0);
    -webkit-transition: all 0.7s ease-in-out 0s;
    transition: all 0.7s ease-in-out 0s;
}

li > a:hover:before {
    visibility: visible;
    -webkit-transform: scaleX(1);
    transform: scaleX(1);
}

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<nav id="nav">
		<ul>
		  <li id="about"><a href="#">About</a></li>
			<li id="work"><a href="#">Work</a></li>
			<li id="contact"><a href="#">Contact</a></li>
		</ul>
</nav>

＆＃13;

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Answer 1

将bottom: 0更改为bottom: -3px;以获得您想要的内容：

ul {
    list-style-type: none;
    margin: 0;
    padding: 0;
	  text-align: right;
	  line-height: 10vh;
	  margin-right: 10vh;
	  animation: fadein 5s;
    -moz-animation: fadein 5s; /* Firefox */
    -webkit-animation: fadein 5s; /* Safari and Chrome */
    -o-animation: fadein 5s; /* Opera */
    font-family: verdana;
}

li {
    display: inline;
    margin-left: 2.5vh;
	  margin-right: 5vh;
	  text-transform: uppercase;
}

a {
	  text-decoration:none;
	  color: white;
}

li > a {
	  position: relative;
  	color: black;
  	text-decoration: none;
}

li > a:hover {
    color: black;
}

li > a:before {
    content: "";
    position: absolute;
    width: 100%;
    height: 2px;
    padding-bottom: 3px;
    bottom: -3px;
    left: 0;
    background-color: black;
    visibility: hidden;
    -webkit-transform: scaleX(0);
    transform: scaleX(0);
    -webkit-transition: all 0.7s ease-in-out 0s;
    transition: all 0.7s ease-in-out 0s;
}

li > a:hover:before {
    visibility: visible;
    -webkit-transform: scaleX(1);
    transform: scaleX(1);
}

<nav id="nav">
		<ul>
		  <li id="about"><a href="#">About</a></li>
			<li id="work"><a href="#">Work</a></li>
			<li id="contact"><a href="#">Contact</a></li>
		</ul>
</nav>

Answer 2

或者将“padding-bottom”添加到“li＆gt; a”。工作得很好。 ：）

ul {
    list-style-type: none;
    margin: 0;
    padding: 0;
	  text-align: right;
	  line-height: 10vh;
	  margin-right: 10vh;
	  animation: fadein 5s;
    -moz-animation: fadein 5s; /* Firefox */
    -webkit-animation: fadein 5s; /* Safari and Chrome */
    -o-animation: fadein 5s; /* Opera */
    font-family: verdana;
}

li {
    display: inline;
    margin-left: 2.5vh;
	  margin-right: 5vh;
	  text-transform: uppercase;
}

a {
	  text-decoration:none;
	  color: white;
}

li > a {
	  position: relative;
  	color: black;
  	text-decoration: none;
    padding-bottom: 10px;
}

li > a:hover {
    color: black;
}

li > a:after {
    content: "";
    position: absolute;
    width: 100%;
    height: 2px;
    padding-bottom: 3px;
    bottom: 0;
    left: 0;
    background-color: black;
    visibility: hidden;
    -webkit-transform: scaleX(0);
    transform: scaleX(0);
    -webkit-transition: all 0.7s ease-in-out 0s;
    transition: all 0.7s ease-in-out 0s;
}

li > a:hover:after {
    visibility: visible;
    -webkit-transform: scaleX(1);
    transform: scaleX(1);
}

<nav id="nav">
		<ul>
		  <li id="about"><a href="#">About</a></li>
			<li id="work"><a href="#">Work</a></li>
			<li id="contact"><a href="#">Contact</a></li>
		</ul>
</nav>