checkbox 更改样式

<div class="wrap">
<p>1. 勾选</p>
<input type="checkbox" id="checkbox_a1" class="chk_1" checked /><label for="checkbox_a1"></label>
<input type="checkbox" id="checkbox_a2" class="chk_1" /><label for="checkbox_a2"></label>
</div>

.chk_1{
display: none;
}/*******STYLE 1*******/
.chk_1 + label {
background-color: #FFF;
border: 1px solid #C1CACA;
box-shadow: 0 1px 2px rgba(0, 0, 0, 0.05), inset 0px -15px 10px -12px rgba(0, 0, 0, 0.05);
padding: 9px;
border-radius: 5px;
display: inline-block;
position: relative;
margin-right: 30px;
}
.chk_1 + label:active {
box-shadow: 0 1px 2px rgba(0,0,0,0.05), inset 0px 1px 3px rgba(0,0,0,0.1);
}.chk_1:checked + label {
background-color: #ECF2F7;
border: 1px solid #92A1AC;
box-shadow: 0 1px 2px rgba(0, 0, 0, 0.05), inset 0px -15px 10px -12px rgba(0, 0, 0, 0.05), inset 15px 10px -12px rgba(255, 255, 255, 0.1);
color: #243441;
}.chk_1:checked + label:after {
content: '\2714';
position: absolute;
top: 0px;
left: 0px;
color: #758794;
width: 100%;
text-align: center;
font-size: 1.4em;
padding: 1px 0 0 0;
vertical-align: text-top;
}