Create simple CSS modal window - html

Question

The goal is to create a simple and CSS-only modal window (popup), when the user clicks a link.
With no dependencies or any kind of script, and with as less code as possible.

Answer 1

.box {
width: 40%;
margin: 0 auto;
background: rgba(255,255,255,0.2);
padding: 35px;
border: 2px solid #fff;
border-radius: 20px/50px;
background-clip: padding-box;
text-align: center;
}
.overlay {
position: fixed;
top: 0;
bottom: 0;
left: 0;
right: 0;
background: rgba(0, 0, 0, 0.7);
transition: opacity 500ms;
visibility: hidden;
opacity: 0;
}
.overlay:target {
visibility: visible;
opacity: 1;
}
.popup {
margin: 70px auto;
padding: 20px;
background: #fff;
border-radius: 5px;
width: 30%;
position: relative;
transition: all 5s ease-in-out;
}
.popup .close {
position: absolute;
top: 20px;
right: 30px;
transition: all 200ms;
font-size: 30px;
font-weight: bold;
text-decoration: none;
color: #333;
}
<div class="box">
<a class="button" href="#popup1">Open</a>
</div>
<div id="popup1" class="overlay">
<div class="popup">
<h2>Here i am</h2>
<a class="close" href="#">×</a>
</div>
</div>

Answer 2

I created this simple modal window:
.exit-intent {
opacity: 0;
visibility: hidden;
position: fixed;
top: 0;
right: 0;
bottom: 0;
left: 0;
text-align: center;
background-color: rgba(255, 255, 255, .8);
z-index: 7;
display: flex;
flex-direction: column;
height: 100vh;
overflow-y: auto
}
.exit-intent {
position: fixed;
max-width: 500px;
border-radius: 10px;
background: rgba(255, 255, 255, 0.9);
visibility: hidden;
opacity: 0;
z-index: 1;
}
.exit-intent:target {
visibility: visible;
opacity: 1;
}
.exit-intent-close {
position: absolute;
max-width: 500px;
border-radius: 10px;
background: rgba(255, 255, 255, 0.9);
}
.exit-intent .close {
position: absolute;
right: 5px;
top: 5px;
padding: 5px;
color: #000;
font-size: 2em;
line-height: 0.6em;
font-weight: bold;
}
.exit-intent .close:hover {
color: #999;
}
.close-exit-intent {
background: rgba(0, 0, 0, 0.7);
cursor: default;
position: fixed;
top: 0;
left: 0;
right: 0;
bottom: 0;
opacity: 0;
visibility: hidden;
}
.exit-intent:target+.close-exit-intent {
opacity: 1;
visibility: visible;
}
Link
<div id="exit-intent" class="exit-intent">
×
<h2>Window</h2>
</div>