/* Reset */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body {
    font-family: "Segoe UI", Tahoma, Geneva, Verdana, sans-serif;
    display: flex;
    flex-direction: column;
    align-items: center;
    min-height: 100%;
    background: #ffffff;
}

#library {
    
    height: auto;
    display: block;
}

.button-container {
    display: flex;
    justify-content: center;
    gap: 20px;
    margin: 20px 0;
}

.button {
    padding: 12px 25px;
    font-size: 16px;
    font-weight: bold;
    color: #fff;
    border: none;
    border-radius: 8px;
    cursor: pointer;
    transition: 0.3s ease;
    text-transform: uppercase;
}

#login {
    background: #28a745;
}
#login:hover {
    background: #218838;
}

#registration {
    background: #007bff;
}
#registration:hover {
    background: #0069d9;
}
.overdue {
    background: #ffe6e6 !important;
    color: #e74c3c;
    font-weight: bold;
}