:root {
        --color-background: #ffffff;
        --color-primary: #1d1d1f;
        --color-secondary: #6e6e73;
        --color-white: #ffffff;
        --color-light-gray: #f2f2f7;
        --color-hover-bg: rgba(29, 29, 31, 0.05);
        --color-hover-primary: #0a84ff;
        --color-hover-success: #34c759;
        --color-hover-warning: #ffcc00;
        --color-hover-danger: #ff3b30;
        --border-radius: 12px;
        --font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
        --font-size-base: 17px;
        --font-size-lg: 1.375rem;
        --font-size-sm: 0.875rem;
        --line-height: 1.8;
        --box-shadow: none;
        --box-shadow-hover: 0 4px 12px rgba(0, 0, 0, 0.05);
        --transition-speed: 0.3s;
        --spacing-small: 5px;
        --spacing-medium: 15px;
        --spacing-large: 20px;
        --spacing-xlarge: 40px;
    }

    /* Global Styles */
    *, *::before, *::after {
        box-sizing: border-box;
        transition: all var(--transition-speed) ease-in-out;
    }

    body {
        background-color: var(--color-background);
        font-family: var(--font-family);
        color: var(--color-primary);
        margin: 0;
        padding: 0;
        line-height: var(--line-height);
        font-size: var(--font-size-base);
    }

    /* Utility Classes */
    .mt-1 { margin-top: 0.25rem; }
    .mt-2 { margin-top: 0.5rem; }
    .mt-3 { margin-top: 1rem; }
    .mt-4 { margin-top: 1.5rem; }
    .mt-5 { margin-top: 2rem; }

    .pt-4 { padding-top: 1.5rem; }
    .pt-5 { padding-top: 2rem; }

    .mb-0 { margin-bottom: 0; }
    .mb-3 { margin-bottom: 1rem; }
    .mb-4 { margin-bottom: 1.5rem; }
    .mb-5 { margin-bottom: 2rem; }

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

    .flex-center {
        display: flex;
        align-items: center;
        justify-content: center;
    }

    .flex-column {
        display: flex;
        flex-direction: column;
    }

    .gap-20 {
        gap: 20px;
    }

    /* Layout Wrapper to control spacing between navbar and content */
    .layout {
        padding-top: var(--spacing-xlarge);
    }

    /* Container */
    .container {
        width: 100%;
        max-width: 2000px;
        margin: 0 auto;
        padding: 0 var(--spacing-large);
    }

    /* Card Component */
    .card {
        border: 1px solid var(--color-light-gray);
        border-radius: var(--border-radius);
        background-color: var(--color-white);
        overflow: hidden;
        transition: box-shadow var(--transition-speed), transform var(--transition-speed);
        margin-bottom: var(--spacing-large);
        box-shadow: none;
    }

    .card:hover {
        transform: translateY(0);
        box-shadow: var(--box-shadow-hover);
    }

    .card-header {
        background-color: var(--color-white);
        border-bottom: none;
        font-weight: bold;
        font-size: var(--font-size-lg);
        padding: 16px 20px;
    }

    .card-body {
        padding: 20px;
    }

    /* Buttons */
    .btn {
        display: inline-block;
        font-family: inherit;
        font-weight: 500;
        text-align: center;
        cursor: pointer;
        border: 1px solid transparent;
        border-radius: 8px;
        padding: 12px 24px;
        font-size: var(--font-size-sm);
        transition: background-color var(--transition-speed), color var(--transition-speed), transform var(--transition-speed);
        text-decoration: none;
        margin: var(--spacing-small) 0;
        background-color: transparent;
        color: var(--color-primary);
    }

    .btn-primary {
        background-color: var(--color-primary);
        color: var(--color-white);
        border: 1px solid var(--color-primary);
    }

    .btn-primary:hover {
        background-color: var(--color-hover-primary);
        border-color: var(--color-hover-primary);
        transform: scale(1.05);
    }

    .btn-success {
        background-color: #28a745;
        color: var(--color-white);
        border: 1px solid #28a745;
    }

    .btn-success:hover {
        background-color: var(--color-hover-success);
        border-color: var(--color-hover-success);
        transform: scale(1.05);
    }

    .btn-warning {
        background-color: #ffc107;
        color: var(--color-white);
        border: 1px solid #ffc107;
    }

    .btn-warning:hover {
        background-color: var(--color-hover-warning);
        border-color: var(--color-hover-warning);
        transform: scale(1.05);
    }

    .btn-danger {
        background-color: #dc3545;
        color: var(--color-white);
        border: 1px solid #dc3545;
    }

    .btn-danger:hover {
        background-color: var(--color-hover-danger);
        border-color: var(--color-hover-danger);
        transform: scale(1.05);
    }

    .btn-link {
        color: var(--color-primary);
        text-decoration: none;
        background: none;
        padding: 0;
        font-weight: 600;
    }

    .btn-link:hover {
        text-decoration: underline;
        color: var(--color-hover-primary);
    }

    /* Tables */
    .table {
        width: 100%;
        border-collapse: collapse;
        margin-bottom: 1rem;
        overflow-x: auto;
        display: block;
    }

    .table thead th {
        background-color: var(--color-light-gray);
        border-bottom: 1px solid var(--color-light-gray);
        padding: 16px 20px;
        text-align: left;
        font-weight: 600;
        color: var(--color-primary);
    }

    .table tbody td {
        padding: 16px 20px;
        border-bottom: 1px solid var(--color-light-gray);
    }

    .table tbody tr:hover {
        background-color: rgba(0, 0, 0, 0.02);
    }

    /* Navbar */
    .navbar {
        display: flex;
        align-items: center;
        justify-content: space-between;
        padding: 20px 30px;
        background-color: var(--color-white);
        box-shadow: 0 1px 3px rgba(0, 0, 0, 0.1);
        position: sticky;
        top: 0;
        z-index: 1000;
    }

    .navbar-brand {
        font-weight: bold;
        font-size: 1.75rem;
        color: var(--color-primary) !important;
        text-decoration: none;
    }

    .navbar-nav {
        display: flex;
        gap: 35px;
    }

    .navbar-nav a {
        color: var(--color-primary);
        text-decoration: none;
        font-weight: 500;
        transition: color var(--transition-speed), background-color var(--transition-speed);
        padding: 10px 15px;
        border-radius: 6px;
        font-size: 1rem;
    }

    .navbar-nav a:hover {
        color: var(--color-hover-primary);
        background-color: var(--color-hover-bg);
    }

    /* Alerts */
    .alert {
        border-radius: 8px;
        padding: 16px 24px;
        margin: 20px 0;
        font-weight: 500;
        position: relative;
    }

    .alert-success {
        background-color: #d4edda;
        color: #155724;
    }

    .alert-warning {
        background-color: #fff3cd;
        color: #856404;
    }

    .alert-danger {
        background-color: #f8d7da;
        color: #721c24;
    }

    /* Modal */
    .modal-content {
        border-radius: var(--border-radius);
        padding: 20px;
        background-color: var(--color-white);
        box-shadow: var(--box-shadow);
        transition: transform var(--transition-speed);
        max-width: 500px;
        margin: auto;
    }

    .modal-header, .modal-footer {
        padding: 15px 20px;
        border-bottom: 1px solid var(--color-light-gray);
    }

    .modal-header {
        border-bottom: none;
    }

    .modal-title {
        margin: 0;
        font-size: 1.5rem;
        font-weight: bold;
    }

    /* Responsive Design */

    /* Small devices (landscape phones, 576px and up) */
    @media (min-width: 576px) {
        .container {
            padding: 0 20px;
        }

        .btn {
            margin: var(--spacing-small);
        }

        .navbar-nav {
            gap: 20px;
        }
    }

    /* Medium devices (tablets, 768px and up) */
    @media (min-width: 768px) {
        .container {
            max-width: 750px;
        }

        .navbar-nav {
            gap: 25px;
        }

        .btn {
            padding: 12px 28px;
            font-size: 0.9rem;
        }

        .layout {
            padding-top: var(--spacing-medium);
        }
    }

    /* Large devices (desktops, 992px and up) */
    @media (min-width: 992px) {
        .container {
            max-width: 970px;
        }

        .navbar-nav {
            gap: 30px;
        }

        .btn {
            padding: 14px 32px;
            font-size: 1rem;
        }
    }

    /* Extra large devices (large desktops, 1200px and up) */
    @media (min-width: 1200px) {
        .container {
            max-width: 1440px;
        }

        .navbar-nav {
            gap: 35px;
        }

        .btn {
            padding: 16px 40px;
            font-size: 1.1rem;
        }
    }

    /* Additional Responsive Adjustments */

    /* Adjust Navbar for Mobile */
    @media (max-width: 768px) {
        .navbar {
            flex-wrap: wrap;
        }

        .navbar-nav {
            width: 100%;
            justify-content: space-between;
            margin-top: 10px;
            flex-direction: column;
            gap: 10px;
        }

        .navbar-nav a {
            flex: 1 1 auto;
            text-align: center;
            padding: 10px 0;
        }

        .btn {
            width: 100%;
            text-align: center;
        }

        .modal-content {
            width: 95%;
            padding: 15px;
        }
    }

    /* Ensure Tables are Scrollable on Small Screens */
    @media (max-width: 768px) {
        .table {
            display: block;
            overflow-x: auto;
            white-space: nowrap;
        }

        .table thead {
            display: none;
        }

        .table tbody td {
            display: block;
            padding: 10px;
            position: relative;
        }

        .table tbody td::before {
            content: attr(data-label);
            position: absolute;
            left: 10px;
            font-weight: bold;
        }

        .table tbody tr {
            margin-bottom: 15px;
            border-bottom: 2px solid var(--color-light-gray);
        }
    }

    /* Optimize Button Sizes for Touch Devices */
    @media (pointer: coarse) {
        .btn {
            padding: 14px 32px;
            font-size: 1rem;
        }

        .navbar-nav a {
            padding: 12px 0;
        }
    }

    /* Ensure Images are Responsive */
    img {
        max-width: 100%;
        height: auto;
    }

    /* Ensure Modal is Responsive */
    @media (max-width: 576px) {
        .modal-content {
            width: 90%;
            padding: 15px;
        }

        .modal-header, .modal-footer {
            padding: 10px 15px;
        }

        .modal-title {
            font-size: 1.25rem;
        }
    }

    /* Enhance Form Elements for Responsiveness */
    input, select, textarea {
        width: 100%;
        padding: 12px; /* 增加内边距 */
        margin-bottom: 15px;
        border: 1px solid var(--color-light-gray);
        border-radius: 8px;
        font-size: 1rem;
        transition: border-color var(--transition-speed), box-shadow var(--transition-speed);
    }

    input:focus, select:focus, textarea:focus {
        border-color: var(--color-primary);
        box-shadow: 0 0 0 2px rgba(10, 132, 255, 0.2);
        outline: none;
    }
/* Footer Styles */
.footer {
    background-color: var(--color-white);
    border-top: 1px solid var(--color-light-gray);
    padding: var(--spacing-large) 0;
    text-align: center;
    font-size: var(--font-size-sm);
    color: var(--color-secondary);
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
}

.footer p {
    margin: 0;
}

/* Footer Navigation Styles */
.footer-nav {
    margin-top: var(--spacing-small);
    display: flex;
    gap: var(--spacing-medium);
    flex-wrap: wrap;
    justify-content: center;
}

/* Increase gap for larger screens */
@media (min-width: 992px) { /* 大型设备，如桌面 */
    .footer-nav {
        gap: 30px; /* 增加间距 */
    }
}

/* Optional: Add padding to individual links for better spacing */
.footer-nav a {
    color: var(--color-secondary);
    text-decoration: none;
    font-weight: 500;
    transition: color var(--transition-speed);
    padding: 5px 10px; /* 增加内边距 */
}

.footer-nav a:hover {
    color: var(--color-primary);
}

/* Footer Social Media Styles */
.footer-social {
    margin-top: var(--spacing-medium);
    display: flex;
    gap: var(--spacing-small);
}

/* Increase gap for larger screens */
@media (min-width: 992px) { /* 大型设备，如桌面 */
    .footer-social {
        gap: 15px; /* 增加间距 */
    }
}

.footer-social a {
    color: var(--color-secondary);
    text-decoration: none;
    font-size: 1.2rem;
    transition: color var(--transition-speed);
    padding: 5px;
}

.footer-social a:hover {
    color: var(--color-primary);
}

/* Responsive Adjustments for Footer */
@media (max-width: 768px) {
    .footer {
        padding: var(--spacing-medium) 0;
        font-size: 0.8rem;
    }

    .footer-nav {
        gap: var(--spacing-small);
    }

    .footer-social {
        gap: var(--spacing-small);
    }

    /* Stack navigation links vertically on very small screens */
    @media (max-width: 576px) {
        .footer-nav {
            flex-direction: column;
            align-items: center;
        }

        .footer-nav a {
            padding: 8px 0; /* 增加垂直间距 */
        }
    }
}