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CSS

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HTML 

              
                <input type="radio" name="a-0" class="correct" id="a-0-c" /><input type="radio" name="a-0" id="a-0-i-0" /><input type="radio" name="a-0" id="a-0-i-1" /><input type="radio" name="a-0" id="a-0-i-2" />
<input type="radio" name="a-1" class="correct" id="a-1-c" /><input type="radio" name="a-1" id="a-1-i-0" /><input type="radio" name="a-1" id="a-1-i-1" /><input type="radio" name="a-1" id="a-1-i-2" />
<input type="radio" name="a-2" class="correct" id="a-2-c" /><input type="radio" name="a-2" id="a-2-i-0" /><input type="radio" name="a-2" id="a-2-i-1" /><input type="radio" name="a-2" id="a-2-i-2" />
<input type="radio" name="a-3" class="correct" id="a-3-c" /><input type="radio" name="a-3" id="a-3-i-0" /><input type="radio" name="a-3" id="a-3-i-1" /><input type="radio" name="a-3" id="a-3-i-2" />
<input type="radio" name="a-4" class="correct" id="a-4-c" /><input type="radio" name="a-4" id="a-4-i-0" /><input type="radio" name="a-4" id="a-4-i-1" /><input type="radio" name="a-4" id="a-4-i-2" />

<div id="results" class="box">
  <div class="results"><span id="result"></span> correct answers</div>
  <p><a href="#">Restart the game</a></p>
  <div>CSS Trivia developed by Alvaro Montoro</div>
</div>

<div class="options box" id="q-4">
  <div class="question">How many lines of JavaScript code are there in this web game?</div>
  <label for="a-4-c">0</label>
  <label for="a-4-i-0">About 3.50</label>
  <label for="a-4-i-1">42</label>
  <label for="a-4-i-2">734</label>
  <a href="#results">Complete Test</a>
</div>

<div class="options box" id="q-3">
  <div class="question">Can a trivia game be developed only using HTML and CSS (no JS)?</div>
  <label for="a-3-c">Yes</label>
  <label for="a-3-i-0">No</label>
  <label for="a-3-i-1">Maybe</label>
  <label for="a-3-i-2">Inconceivable</label>
  <a href="#q-4">Confirm Answer</a>
</div>

<div class="options box" id="q-2">
  <div class="question">Which of these selectors is correct?</div>
  <label for="a-2-i-0">#class</label>
  <label for="a-2-i-1">.id</label>
  <label for="a-2-i-2">Both are wrong</label>
  <label for="a-2-c">Both are correct</label>
  <a href="#q-3">Confirm Answer</a>
</div>

<div class="options box" id="q-1">
  <div class="question">What does CSS stand for?</div>
  <label for="a-1-i-0">CSS Style Sheet</label>
  <label for="a-1-c">Cascading Style Sheet</label>
  <label for="a-1-i-1">Casual Style Sheet</label>
  <label for="a-1-i-2">Classy Style Sheets</label>
  <a href="#q-2">Confirm Answer</a>
</div>

<div class="options box" id="q-0">
  <div class="question">What year was CSS first released?</div>
  <label for="a-0-i-0">1988</label>
  <label for="a-0-i-1">1992</label>
  <label for="a-0-c">1996</label>
  <label for="a-0-i-2">2000</label>
  <a href="#q-1">Confirm Answer</a>
</div>

<div class="box" id="welcome">
  <h2>CSS Trivia</h2>
  <p>Welcome to CSS Trivia! A small Q&A game developed exclusively with HTML and CSS, and not a single line of JavaScript</p>
  <a href="#q-0">Start Game</a>
</div>
!

CSS 

              
                @import url('https://fonts.googleapis.com/css?family=Dosis|Roboto');

body {
  counter-reset: correct;
}
body input.correct:checked {
  counter-increment: correct;
}
body #results #result::before {
  content: counter(correct);
}

html,
body {
  overflow: hidden;
  user-select: none;
  background: linear-gradient(#99ccff, #6699cc);
  font-family: Dosis, Roboto, sans-serif;
  position: relative;
  height: 100%;
  width: 100%;
  margin: 0;
  padding: 0;
}

.box {
  background: white;
  border-radius: 3px;
  padding: 1em;
  position: absolute;
  top: 50%;
  left: 50%;
  transform: translate(50%, -50%);
  -webkit-transform: translate(50%, -50%);
  -moz-transform: translate(50%, -50%);
  width: 400px;
  z-index: 0;
  opacity: 0;
  transition: all 1s;
  box-shadow: 0 1.5em 0.5em -1em rgba(0, 0, 0, 0.25);
}

#welcome,
.box:target {
  transform: translate(-50%, -50%);
  -webkit-transform: translate(-50%, -50%);
  -moz-transform: translate(-50%, -50%);
  z-index: 1;
  opacity: 1;
}

#q-0:target ~ #welcome,
#q-1:target ~ #welcome,
#q-2:target ~ #welcome,
#q-3:target ~ #welcome,
#q-4:target ~ #welcome,
#results:target ~ #welcome,
#q-1:target ~ #q-0,
#q-2:target ~ #q-1,
#q-3:target ~ #q-2,
#q-4:target ~ #q-3,
#results:target ~ #q-4 {
  transform: translate(-200%, -50%);
  opacity: 0;
}

label,
.box > a {
  background: linear-gradient(#336699, #003366);
  width: 49%;
  margin: 0.5%;
  margin-bottom: 0.5%;
  display: block;
  float: left;
  border-radius: 2px;
  padding: 0.33em;
  box-sizing: border-box;
  border: 1px solid #003366;
  color: white;
  cursor: pointer;
  font-size:0.9em;
}

label:hover {
  background: linear-gradient(#225588, #002255);
}

label::before {
  padding-right: 0.33em;
  margin-right: 0.33em;
  border-right: 1px solid rgba(0, 0, 0, 0.3);
}

label:nth-child(2)::before {
  content: "A";
}
label:nth-child(3)::before {
  content: "B";
}
label:nth-child(4)::before {
  content: "C";
}
label:nth-child(5)::before {
  content: "D";
}

#a-0-c:checked ~ #q-0 [for="a-0-c"],
#a-0-i-0:checked ~ #q-0 [for="a-0-i-0"],
#a-0-i-1:checked ~ #q-0 [for="a-0-i-1"],
#a-0-i-2:checked ~ #q-0 [for="a-0-i-2"],
#a-1-c:checked ~ #q-1 [for="a-1-c"],
#a-1-i-0:checked ~ #q-1 [for="a-1-i-0"],
#a-1-i-1:checked ~ #q-1 [for="a-1-i-1"],
#a-1-i-2:checked ~ #q-1 [for="a-1-i-2"],
#a-2-c:checked ~ #q-2 [for="a-2-c"],
#a-2-i-0:checked ~ #q-2 [for="a-2-i-0"],
#a-2-i-1:checked ~ #q-2 [for="a-2-i-1"],
#a-2-i-2:checked ~ #q-2 [for="a-2-i-2"],
#a-3-c:checked ~ #q-3 [for="a-3-c"],
#a-3-i-0:checked ~ #q-3 [for="a-3-i-0"],
#a-3-i-1:checked ~ #q-3 [for="a-3-i-1"],
#a-3-i-2:checked ~ #q-3 [for="a-3-i-2"],
#a-4-c:checked ~ #q-4 [for="a-4-c"],
#a-4-i-0:checked ~ #q-4 [for="a-4-i-0"],
#a-4-i-1:checked ~ #q-4 [for="a-4-i-1"],
#a-4-i-2:checked ~ #q-4 [for="a-4-i-2"] {
  background: linear-gradient(#ffee66, #ccbb33);
  border: 1px solid #ccbb33;
  color: #333333;
}

.box h2,
.box .question,
#results > div.results {
  margin: 0;
  padding: 0;
  font-size: 1.4em;
  font-weight: bold;
  margin-bottom: 1em;
}

.box > a {
  float: right;
  margin-top: 1em;
  text-align: center;
  text-decoration: none;
  background: linear-gradient(#33dd66, #00aa33);
  border: 1px solid #00aa33;
  color: #ffffff;
  cursor: pointer;
}

.box > a:hover {
  background: linear-gradient(#22cc55, #009922);
}

#results {
  text-align: center;
}

input {
  position: absolute;
  top: -1000px;
}
!

JS
!
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