@import url(https://fonts.googleapis.com/css?family=Open+Sans:400);
.frame {
    position: absolute;
    top: 50%;
    left: 50%;
    width: 400px;
    height: 400px;
    margin-top: -200px;
    margin-left: -200px;
    border-radius: 2px;
    box-shadow: 1px 2px 10px 0px rgba(0, 0, 0, 0.3);
    overflow: hidden;
    background: #1abc9c;
    color: #fff;
    font-family: 'Open Sans', Helvetica, sans-serif;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

.center {
    position: absolute;
    top: 50%;
    left: 50%;
    -webkit-transform: translate(-50%, -50%);
    transform: translate(-50%, -50%);
}

.input {
    display: none;
}

.button {
    position: relative;
    box-sizing: border-box;
    display: inline-block;
    width: 30px;
    height: 30px;
    border-radius: 50px;
    margin: 5px;
    background: none;
    border: 1px solid #fff;
    color: #fff;
    cursor: pointer;
    text-align: center;
    font-size: 16px;
    font-weight: 400;
    line-height: 27px;
    -webkit-transition: all .5s ease-in-out;
    transition: all .5s ease-in-out;
}
.button:hover {
    background: #16a085;
    -webkit-transition: all .3s ease-in-out;
    transition: all .3s ease-in-out;
}
.button:before {
    display: block;
    content: '';
    position: absolute;
    z-index: -1;
    top: -1px;
    left: -1px;
    right: -1px;
    bottom: -1px;
    border-radius: 50%;
    background: #fff;
    -webkit-transform: scale(0);
    transform: scale(0);
    -webkit-transition: all .5s ease-in-out;
    transition: all .5s ease-in-out;
}

#input-1:checked ~ .button-1 {
    color: #1abc9c;
    background: none;
    -webkit-transition: all .5s ease-in-out;
    transition: all .5s ease-in-out;
}
#input-1:checked ~ .button-1:before {
    -webkit-transform: scale(1);
    transform: scale(1);
}

#input-2:checked ~ .button-2 {
    color: #1abc9c;
    background: none;
    -webkit-transition: all .5s ease-in-out;
    transition: all .5s ease-in-out;
}
#input-2:checked ~ .button-2:before {
    -webkit-transform: scale(1);
    transform: scale(1);
}

#input-3:checked ~ .button-3 {
    color: #1abc9c;
    background: none;
    -webkit-transition: all .5s ease-in-out;
    transition: all .5s ease-in-out;
}
#input-3:checked ~ .button-3:before {
    -webkit-transform: scale(1);
    transform: scale(1);
}

#input-4:checked ~ .button-4 {
    color: #1abc9c;
    background: none;
    -webkit-transition: all .5s ease-in-out;
    transition: all .5s ease-in-out;
}
#input-4:checked ~ .button-4:before {
    -webkit-transform: scale(1);
    transform: scale(1);
}