body {
    /* background-image: url(); */
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 100vh;
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
}

.container {
    background: #878383;
    width: 350px;
    padding: 40px;
    border-radius: 10px;
    box-shadow: 0 4px 8px 0 rgba(0,0,0,0.2);
    overflow: hidden;
}

h2 {
    color: #ffffff;
    text-align: center;
    margin-bottom: 30px;
}

.user-box {
    position: relative;
    margin-bottom: 20px;
}

.user-box input {
    width: 100%;
    padding: 10px 0;
    font-size: 16px;
    color: #ffffff;
    background: transparent;
    border: none;
    border-bottom: 1px solid #ffffff;
    outline: none;
}

.user-box label {
    position: absolute;
    top: 0;
    left: 0;
    pointer-events: none;
    transition: 0.5s;
}

.user-box input:focus ~ label,
.user-box input:valid ~ label {
    top: -15px;
    font-size: 12px;
    color: #ffffff;
}

form button {
    background: #2196F3;
    border: none;
    color: #ffffff;
    padding: 15px 20px;
    text-align: center;
    text-decoration: none;
    display: inline-block;
    font-size: 16px;
    cursor: pointer;
    width: 100%;
    border-radius: 5px;
    box-shadow: 0 4px 8px 0 rgba(0,0,0,0.2);
    transition: 0.3s;
}

form button:hover {
    background: #007bff;
    box-shadow: 0 6px 12px 0 rgba(0,0,0,0.2);
}

form button span {
    position: absolute;
    left: 0;
    top: 50%;
    transform: translateY(-50%);
    width: 0;
    height: 2px;
    background: #ffffff;
    transition: 0.3s;
}

form button span:first-child {
    left: 0;
}

form button span:nth-child(2) {
    left: 20%;
}

form button span:nth-child(3) {
    left: 40%;
}

form button span:nth-child(4) {
    left: 60%;
}

form button:hover span {
    width: 100%;
}

form button:focus {
    outline: none;
}

.login-box {
    text-align: center;
}