How to make my slider responsive - css

Question

I have a problem and this isn't really my area and am not able to find a good solution, please help me. I want to make my slider on my website responsive. Do you have any idea how I should do it?
The slider needs to be smaller or be shaped differently when I make the window smaller. Can I use the #media rule or is it something else I should do?
Thanx for helping a beginner like me:)!
<ul class="slides">
<input type="radio" name="radio-btn" id="img-1" checked />
<li class="slide-container">
<div class="slide">
<img src="bilder/blommor.jpg" />
</div>
<div class="nav">
<label for="img-6" class="prev">‹</label>
<label for="img-2" class="next">›</label>
</div>
</li>
<input type="radio" name="radio-btn" id="img-2" />
<li class="slide-container">
<div class="slide">
<img src="bilder/Berg.jpg" />
</div>
<div class="nav">
<label for="img-1" class="prev">‹</label>
<label for="img-3" class="next">›</label>
</div>
</li>
<input type="radio" name="radio-btn" id="img-3" />
<li class="slide-container">
<div class="slide">
<img src="bilder/water.jpg" />
</div>
<div class="nav">
<label for="img-2" class="prev">‹</label>
<label for="img-4" class="next">›</label>
</div>
</li>
<input type="radio" name="radio-btn" id="img-4" />
<li class="slide-container">
<div class="slide">
<img src="bilder/ros.jpg" />
</div>
<div class="nav">
<label for="img-3" class="prev">‹</label>
<label for="img-5" class="next">›</label>
</div>
</li>
<input type="radio" name="radio-btn" id="img-5" />
<li class="slide-container">
<div class="slide">
<img src="bilder/glasogon.jpg" />
</div>
<div class="nav">
<label for="img-4" class="prev">‹</label>
<label for="img-6" class="next">›</label>
</div>
</li>
<li class="nav-dots">
<label for="img-1" class="nav-dot" id="img-dot-1"></label>
<label for="img-2" class="nav-dot" id="img-dot-2"></label>
<label for="img-3" class="nav-dot" id="img-dot-3"></label>
<label for="img-4" class="nav-dot" id="img-dot-4"></label>
<label for="img-5" class="nav-dot" id="img-dot-5"></label>
</li>
Css:
#import url(https://fonts.googleapis.com/css?family=Varela+Round);
html, body { background: #333 url("https://codepen.io/images/classy_fabric.png"); }
.slides {
padding: 0;
width: 609px;
height: 420px;
display: block;
margin: 0 auto;
position: relative;
}
.slides * {
user-select: none;
-ms-user-select: none;
-moz-user-select: none;
-khtml-user-select: none;
-webkit-user-select: none;
-webkit-touch-callout: none;
}
.slides input { display: none; }
.slide-container { display: block; }
.slide {
top: 0;
opacity: 0;
width: 609px;
height: 420px;
display: block;
position: absolute;
transform: scale(0);
transition: all .7s ease-in-out;
}
.slide img {
width: 100%;
height: 100%;
}
.nav label {
width: 200px;
height: 100%;
display: none;
position: absolute;
opacity: 0;
z-index: 9;
cursor: pointer;
transition: opacity .2s;
color: #FFF;
font-size: 156pt;
text-align: center;
line-height: 380px;
font-family: "Varela Round", sans-serif;
background-color: rgba(255, 255, 255, .3);
text-shadow: 0px 0px 15px rgb(119, 119, 119);
}
.slide:hover + .nav label { opacity: 0.5; }
.nav label:hover { opacity: 1; }
.nav .next { right: 0; }
input:checked + .slide-container .slide {
opacity: 1;
transform: scale(1);
transition: opacity 1s ease-in-out;
}
input:checked + .slide-container .nav label { display: block; }
.nav-dots {
width: 100%;
bottom: 9px;
height: 11px;
display: block;
position: absolute;
text-align: center;
}
.nav-dots .nav-dot {
top: -5px;
width: 11px;
height: 11px;
margin: 0 4px;
position: relative;
border-radius: 100%;
display: inline-block;
background-color: rgba(0, 0, 0, 0.6);
}
.nav-dots .nav-dot:hover {
cursor: pointer;
background-color: rgba(0, 0, 0, 0.8);
}
input#img-1:checked ~ .nav-dots label#img-dot-1,
input#img-2:checked ~ .nav-dots label#img-dot-2,
input#img-3:checked ~ .nav-dots label#img-dot-3,
input#img-4:checked ~ .nav-dots label#img-dot-4,
input#img-5:checked ~ .nav-dots label#img-dot-5,
input#img-6:checked ~ .nav-dots label#img-dot-6 {
background: rgba(0, 0, 0, 0.8);
}