Modal Window functionality using only CSS - html

Question

I wanted to display a modal window on clicking on the buttons by using only css.
So far everything works but expect one thing. When i click anywhere out side the modal window, i need to close the modal box which is not happenig now. Is there any way we can do it only using css ? Please help
.modalDialog {
position: fixed;
font-family: Arial, Helvetica, sans-serif;
top: 0;
right: 0;
bottom: 0;
left: 0;
background: rgba(0, 0, 0, 0.8);
z-index: 99999;
opacity: 0;
/* -webkit-transition: opacity 400ms ease-in;
-moz-transition: opacity 400ms ease-in;
transition: opacity 400ms ease-in;*/
pointer-events: none;
}
.modalDialog:target {
opacity: 1;
pointer-events: auto;
}
.modalDialog>div {
width: 400px;
position: relative;
margin: 10% auto;
padding: 5px 20px 13px 20px;
border-radius: 10px;
background: #fff;
background: -moz-linear-gradient(#fff, #999);
background: -webkit-linear-gradient(#fff, #999);
background: -o-linear-gradient(#fff, #999);
}
.close {
background: #606061;
color: #FFFFFF;
line-height: 25px;
position: absolute;
right: -12px;
text-align: center;
top: -10px;
width: 24px;
text-decoration: none;
font-weight: bold;
-webkit-border-radius: 12px;
-moz-border-radius: 12px;
border-radius: 12px;
-moz-box-shadow: 1px 1px 3px #000;
-webkit-box-shadow: 1px 1px 3px #000;
box-shadow: 1px 1px 3px #000;
}
.close:hover {
background: #00d9ff;
}
<div class="cta-module bottom-divider">
<h2>Looking for Health EFPPOS Solutions?</h2>
<div class="cta-wrapper">
<p>Our mobile EFTPOS facilities are convenient, portable and secure</p>
<p><a class="button_primary" href="#openModal">Apply</a></p>
<p><a class="button_secondary" href="#openModal">Learn more</a></p>
</div>
</div>
<div id="openModal" class="modalDialog">
<div>
X
<h2>Modal Box</h2>
<p>This is a sample modal box that can be created</p>
<p>Whether it's a new or second-hand car, a personal loan can help you pay for your car if you don't have the funds up front.</p>
</div>
</div>