:root {
    --background-color: #f8f9fa; /* Light background */
    --card-background: #ffffff;   /* Card background */
    --text-color: #212529;       /* Dark text */
    --heading-color: #0056b3;    /* Primary Blue */
    --secondary-heading-color: #007bff; /* Lighter Blue */
    --border-color: #dee2e6;    /* Subtle border */
    --shadow-color: rgba(0, 86, 179, 0.08); /* Blueish shadow */
    --accent-color: #ffc107; /* Accent Yellow */
    --icon-color: var(--heading-color);
    --grid-gap: 1.5rem;
    --border-radius: 16px; /* Slightly larger radius */
    --transition-speed: 0.3s;
}

/* Dark Theme Variables */
body.dark-theme {
    --background-color: #1a1a1a;
    --card-background: #2c2c2c;
    --text-color: #e0e0e0;
    --heading-color: #4dabf7; /* Lighter Blue for dark mode */
    --secondary-heading-color: #74c0fc;
    --border-color: #444;
    --shadow-color: rgba(0, 0, 0, 0.2);
    --icon-color: var(--heading-color);
}

body {
    font-family: 'Noto Sans SC', sans-serif;
    margin: 0;
    padding: 0;
    background-color: var(--background-color);
    color: var(--text-color);
    line-height: 1.7; /* Slightly increased line height */
    transition: background-color var(--transition-speed) ease, color var(--transition-speed) ease;
    overflow-x: hidden; /* Prevent horizontal scroll */
}

header {
    text-align: center;
    padding: 2rem 1rem;
    background-color: var(--card-background);
    margin-bottom: var(--grid-gap);
    border-bottom: 1px solid var(--border-color);
    position: relative; /* For theme toggle positioning */
}

header h1 {
    color: var(--heading-color);
    margin-bottom: 0.5rem;
    font-weight: 700;
    display: inline-flex; /* Align icon with text */
    align-items: center;
    gap: 0.5rem;
    transition: color var(--transition-speed) ease;
}

main.bento-grid {
    display: grid;
    gap: var(--grid-gap);
    padding: 0 var(--grid-gap) var(--grid-gap);
    /* More dynamic grid layout */
    grid-template-columns: repeat(12, 1fr); /* 12 column grid */
    grid-auto-rows: minmax(150px, auto); /* Min height for rows */
}

.bento-item {
    background-color: var(--card-background);
    padding: 1.8rem; /* Slightly more padding */
    border-radius: var(--border-radius);
    border: 1px solid var(--border-color);
    box-shadow: 0 6px 20px var(--shadow-color);
    transition: transform var(--transition-speed) ease,
                box-shadow var(--transition-speed) ease,
                background-color var(--transition-speed) ease,
                border-color var(--transition-speed) ease;
    position: relative; /* Needed for absolute positioning of the link */
    overflow: hidden; /* Ensure content stays within bounds */
    opacity: 0; /* Initially hidden for scroll animation */
    transform: translateY(20px); /* Initial state for scroll animation */
}

.bento-item.is-visible {
    opacity: 1;
    transform: translateY(0);
}

.bento-item:hover {
    transform: translateY(-5px) scale(1.01); /* Enhanced hover effect */
    box-shadow: 0 10px 30px rgba(0, 86, 179, 0.15);
}
body.dark-theme .bento-item:hover {
     box-shadow: 0 10px 30px rgba(0, 0, 0, 0.3);
}

.bento-item h2 {
    margin-top: 0;
    color: var(--heading-color);
    border-bottom: 2px solid var(--secondary-heading-color);
    padding-bottom: 0.6rem;
    margin-bottom: 1.2rem;
    font-weight: 600; /* Bolder headings */
    font-size: 1.4em;
    display: inline-flex;
    align-items: center;
    gap: 0.6rem; /* Space between icon and text */
    transition: color var(--transition-speed) ease, border-color var(--transition-speed) ease;
}
.bento-item h2 i { /* Style for icons */
    font-size: 1em; /* Adjust icon size relative to h2 */
    color: var(--icon-color);
     transition: color var(--transition-speed) ease;
}

.bento-item h3 {
    color: var(--secondary-heading-color);
    margin-top: 1.8rem;
    margin-bottom: 0.8rem;
    font-weight: 600;
    transition: color var(--transition-speed) ease;
}

.bento-item ul, .bento-item ol {
    padding-left: 0;
    margin-bottom: 0;
    list-style: none;
}

.bento-item ul li, .bento-item ol li {
    margin-bottom: 0.7rem; /* More spacing */
    position: relative;
    padding-left: 1.5em; /* Space for custom bullet */
    font-size: 0.95em;
}

/* Custom bullets */
.bento-item ul li::before {
    content: '▹'; /* Triangle bullet */
    position: absolute;
    left: 0;
    color: var(--secondary-heading-color);
    font-size: 1em;
    top: 0;
     transition: color var(--transition-speed) ease;
}
.bento-item ol {
     counter-reset: item;
     padding-left: 0;
}
.bento-item ol li {
    padding-left: 1.8em;
}
.bento-item ol li::before {
    content: counter(item);
    counter-increment: item;
    position: absolute;
    left: 0;
    background-color: var(--secondary-heading-color);
    color: var(--card-background);
    border-radius: 50%;
    width: 1.2em;
    height: 1.2em;
    line-height: 1.2em;
    text-align: center;
    font-size: 0.8em;
    font-weight: bold;
    top: 0.15em;
     transition: background-color var(--transition-speed) ease, color var(--transition-speed) ease;
}

/* Style for the nested grid-like content */
.feature-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(180px, 1fr)); /* Slightly larger min */
    gap: 1.2rem;
    margin-top: 1.2rem;
}

.feature-item {
    background-color: var(--background-color);
    padding: 1rem;
    border-radius: calc(var(--border-radius) * 0.75); /* Smaller radius */
    border: 1px solid var(--border-color);
    transition: background-color var(--transition-speed) ease, border-color var(--transition-speed) ease;
}

.feature-item h4 {
    margin: 0 0 0.6rem 0;
    font-size: 1em; /* Slightly larger */
    font-weight: 600;
    color: var(--heading-color);
     transition: color var(--transition-speed) ease;
}

.feature-item ul {
    font-size: 0.9em;
    margin: 0;
    padding: 0;
    list-style: none;
}

.feature-item ul li {
    margin-bottom: 0.4rem;
    padding-left: 0;
}
.feature-item ul li::before {
    content: none; /* No bullets for inner items */
}

/* Spanning items (Example - adjust classes in HTML) */
.g-col-span-3 { grid-column: span 3; }
.g-col-span-4 { grid-column: span 4; }
.g-col-span-5 { grid-column: span 5; }
.g-col-span-6 { grid-column: span 6; }
.g-col-span-7 { grid-column: span 7; }
.g-col-span-8 { grid-column: span 8; }
.g-col-span-9 { grid-column: span 9; }
.g-col-span-12 { grid-column: span 12; }

footer {
    text-align: center;
    padding: 1.5rem 1rem;
    margin-top: var(--grid-gap);
    background-color: var(--card-background);
    color: #6c757d; /* Lighter text for footer */
    font-size: 0.9em;
    border-top: 1px solid var(--border-color);
    position: relative; /* For theme toggle positioning */
}
body.dark-theme footer {
    color: #aaa;
}

/* Timeline Interactivity */
.timeline-nav {
    display: flex;
    margin-bottom: 1rem;
    border-bottom: 1px solid var(--border-color);
}

.timeline-nav button {
    padding: 0.8rem 1.5rem;
    border: none;
    background: none;
    cursor: pointer;
    font-size: 1em;
    font-weight: 500;
    color: var(--text-color);
    border-bottom: 3px solid transparent;
    transition: border-color var(--transition-speed) ease, color var(--transition-speed) ease;
    margin-bottom: -1px; /* Overlap border */
}

.timeline-nav button.active {
    color: var(--heading-color);
    border-bottom-color: var(--heading-color);
}
.timeline-nav button:hover:not(.active) {
    color: var(--heading-color);
}

.timeline-content {
    display: none; /* Hide content by default */
    animation: fadeIn 0.5s ease;
}

.timeline-content.active {
    display: block; /* Show active content */
}

@keyframes fadeIn {
    from { opacity: 0; transform: translateY(10px); }
    to { opacity: 1; transform: translateY(0); }
}

.timeline-content h3 {
     margin-top: 0; /* Remove extra top margin */
}

/* Theme Toggle Button */
.theme-toggle {
    position: absolute;
    top: 1rem;
    right: 1rem;
    background: none;
    border: 1px solid var(--border-color);
    border-radius: 50%;
    width: 40px;
    height: 40px;
    cursor: pointer;
    display: flex;
    justify-content: center;
    align-items: center;
    font-size: 1.2rem;
    color: var(--text-color);
    transition: background-color var(--transition-speed) ease, border-color var(--transition-speed) ease, color var(--transition-speed) ease, transform var(--transition-speed) ease;
}
.theme-toggle:hover {
    background-color: rgba(128, 128, 128, 0.1);
    transform: scale(1.1);
}
.theme-toggle .icon-sun { display: block; }
.theme-toggle .icon-moon { display: none; }

body.dark-theme .theme-toggle .icon-sun { display: none; }
body.dark-theme .theme-toggle .icon-moon { display: block; }

/* Responsive adjustments */
@media (max-width: 1200px) {
    .g-col-span-7, .g-col-span-8, .g-col-span-9 { grid-column: span 6; }
}

@media (max-width: 992px) {
    :root { --grid-gap: 1rem; }
    main.bento-grid { grid-template-columns: repeat(6, 1fr); } /* Switch to 6 columns */
    .g-col-span-3, .g-col-span-4, .g-col-span-5, .g-col-span-6, .g-col-span-7, .g-col-span-8, .g-col-span-9, .g-col-span-12 {
        grid-column: span 6; /* Most items span full width */
    }
    /* Allow some side-by-side on medium screens */
    .bento-item.medium-span-3 {
        grid-column: span 3;
    }
     .bento-item.medium-span-6 {
        grid-column: span 6;
    }
    .bento-item { padding: 1.5rem; }
}

@media (max-width: 768px) {
    main.bento-grid { grid-template-columns: 1fr; } /* Stack all on small screens */
     .g-col-span-3, .g-col-span-4, .g-col-span-5, .g-col-span-6, .g-col-span-7, .g-col-span-8, .g-col-span-9, .g-col-span-12,
     .bento-item.medium-span-3, .bento-item.medium-span-6 {
        grid-column: span 1; /* Full width */
    }
    .bento-item { padding: 1.2rem; }
    .feature-grid { grid-template-columns: 1fr; }
    header h1 { font-size: 1.8em; }
    header p { font-size: 0.95em;}
    .timeline-nav button { padding: 0.6rem 1rem; font-size: 0.9em;}
    nav.main-nav {
        height: auto;
        padding: 0.5rem 0;
        position: relative; /* 设置为相对定位，供汉堡菜单按钮定位 */
        flex-direction: column;
        align-items: flex-start;
    }
    
    nav.main-nav ul {
        flex-direction: column;
        align-items: flex-start;
        padding: 0.5rem;
        height: auto;
        display: none; /* 默认隐藏菜单 */
        width: 100%; /* 确保菜单撑满整个导航宽度 */
    }
    
    nav.main-nav ul.show {
        display: flex; /* 当添加show类时显示菜单 */
    }
    
    nav.main-nav li {
        width: 100%;
    }
    
    nav.main-nav a {
        display: block;
        padding: 0.8rem 1rem;
        width: 100%;
    }
    
    .nav-logo-item {
        margin-right: 0;
        padding: 0.5rem;
        display: flex;
        width: 100%;
        justify-content: center;
    }
    
    /* 添加汉堡菜单按钮 */
    .mobile-menu-toggle {
        display: block;
        position: absolute;
        right: 1rem;
        top: 1rem;
        font-size: 1.5rem;
        background: none;
        border: none;
        color: var(--text-color);
        cursor: pointer;
        z-index: 10;
        padding: 0.3rem 0.5rem;
    }
    
    /* 确保汉堡菜单和Logo一行显示 */
    .nav-logo-container {
        display: flex;
        justify-content: center;
        width: 100%;
        margin: 0.5rem 0;
    }
}

/* 桌面版时隐藏汉堡菜单按钮 */
.mobile-menu-toggle {
    display: none;
}

@media (max-width: 480px) {
    :root { --border-radius: 12px; }
    .bento-item { padding: 1rem; }
    header h1 { font-size: 1.6em; }
    nav.main-nav ul { gap: 0.8rem; } /* Further reduce gap */
    .nav-logo { height: 26px; } /* 更小屏幕上进一步减小logo */
    .nav-logo-item { margin-right: 0.5rem; } /* 减小间距 */
}

/* Add styles for the full-item link */
.bento-item .bento-link {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    z-index: 1; /* Place link above content visually, but below interactive elements if needed */
    /* Make it invisible but clickable */
    opacity: 0;
    background: transparent;
     /* Optional: enhance hover slightly on the whole card via link */
    /* transition: background-color 0.2s ease; */
}
/* Ensure link doesn't interfere with text selection or other interactions */
.bento-item > *:not(.bento-link) {
    position: relative;
    z-index: 2; /* Keep content above the main link */
}

/* Optional: Style for the summary paragraph */
.bento-summary {
    font-size: 0.9em;
    color: var(--text-color);
    opacity: 0.8;
    margin-top: -0.8rem; /* Adjust spacing below h2 */
    margin-bottom: 1rem;
    transition: color var(--transition-speed) ease, opacity var(--transition-speed) ease;
}

/* --- Bento Item Styling --- */ 

nav.main-nav { /* Simple nav styling */
    background-color: var(--card-background);
    padding: 0;
    margin-bottom: 1.5rem;
    border-bottom: 1px solid var(--border-color);
    box-shadow: 0 2px 5px rgba(0,0,0,0.05);
    display: flex;
    align-items: center;
    height: 50px; /* 减小导航栏高度 */
}

.nav-logo-container {
    display: flex;
    align-items: center;
    height: 100%; /* 与导航栏同高 */
}

.nav-logo-item {
    height: 100%;
    display: flex;
    align-items: center;
    margin-right: 1rem; /* 减小右侧间距 */
    padding: 0 0.5rem;
}

.nav-logo {
    height: 36px; /* 缩小logo高度 */
    width: auto;
    display: block;
    object-fit: contain;
    margin-top: 3px; /* 微调垂直位置 */
}

nav.main-nav ul {
    list-style: none;
    padding: 0;
    margin: 0;
    display: flex;
    align-items: center; /* 垂直居中 */
    justify-content: flex-start; /* 左对齐 */
    gap: 1.5rem;
    flex-grow: 1;
    height: 100%; /* 与导航栏同高 */
}

/* Add padding to the detail page grid container */
main.bento-grid.detail-page-grid {
    padding: 0 var(--grid-gap) var(--grid-gap); /* Keep consistent padding */
    max-width: 1200px; /* Optional: Limit max width for readability on very wide screens */
    margin: 0 auto; /* Center the grid container */
}

/* General link styling for nav, can be overridden */
nav.main-nav a {
    text-decoration: none;
    color: var(--text-color);
    font-weight: 500;
    padding: 0.5rem 0.8rem; /* Add padding for background hover */
    border-radius: 6px; /* Rounded corners for hover background */
    transition: color var(--transition-speed) ease, background-color var(--transition-speed) ease;
}

/* Specific hover/active styling */
nav.main-nav a:hover {
     color: var(--heading-color);
     background-color: rgba(0, 86, 179, 0.05); /* Subtle background on hover */
}
nav.main-nav a.active {
     color: var(--heading-color);
     font-weight: 700; /* Make active link bolder */
     background-color: rgba(0, 86, 179, 0.1); /* Slightly stronger background for active */
}
body.dark-theme nav.main-nav a:hover {
    background-color: rgba(77, 171, 247, 0.1);
}
body.dark-theme nav.main-nav a.active {
     background-color: rgba(77, 171, 247, 0.2);
}

/* --- Footer Link Styling --- */
footer a {
    color: var(--text-color);
    text-decoration: none;
    font-weight: 500;
    padding: 0.3rem 0.6rem;
    border-radius: 4px;
    transition: color var(--transition-speed) ease, background-color var(--transition-speed) ease;
}
footer a:hover {
    color: var(--heading-color);
    background-color: rgba(128, 128, 128, 0.1);
}
body.dark-theme footer a:hover {
     background-color: rgba(255, 255, 255, 0.1);
}
footer a i { /* Ensure icon has a little space */
    margin-right: 0.4em;
}

/* --- Header and Footer --- */