CSS

sliding button css

  <div class="main">
            <div class="group">
                <a href="#" class="two">
                    <span>I AM COOL TOO</span>
                    <div class="bg"></div>
                </button>
                <a href="#" class="one">I AM COOL</a>
            </div>
        </div>

html {
    font-family: 'Inconsolata', monospace;
    font-weight: 700;
    font-size: 20px;
}
html, body {
    height: 100%;
    width: 100%;
    margin: 0;
    background: #2c3e50;
}
.main {
    width: 100%;
    height: 100%;
    background-color: #2c3e50;
}
.group {
    width: 340px;
    height: 40px;
    padding: 10px 40px;
    line-height: 40px;
    position: relative;
    z-index: 1;
    margin-left: auto;
    margin-right: auto;
    margin-top: 100px;
    
}
.one {
    float: left;
    line-height: 40px;
    color: white;
    text-decoration: none;
    transition: 1.0s;
}
.two {
    float: right;
    text-decoration: none;
    line-height: 40px;
    color: #a6afbf;
}
.bg {
    background-color: #e67e22;
    height: 60px;
    width: 190px;
    position: absolute;
    top: 0;
    margin-left: -260px;
    z-index: -1;
    transition: 1.0s;
    border-radius: 5px;
    
}

span:hover + .bg {
    width: 200px;
    margin-left: -40px;
    background: #27ae60;
}

.two > span:hover {
    color: white;
}

.two:hover ~ .one {
    color:#fff;
}
span {
    padding: 10px 0;
    transition: 1.0s;
}