/* ===== CSS Variables ===== */
:root {
    --bg-primary: #0d1117;
    --bg-secondary: #161b22;
    --bg-tertiary: #21262d;
    --bg-card: #161b22;
    --bg-card-hover: #1c2128;
    --border: #30363d;
    --border-light: #21262d;
    --text-primary: #e6edf3;
    --text-secondary: #8b949e;
    --text-tertiary: #6e7681;
    --accent: #58a6ff;
    --accent-hover: #79c0ff;
    --green: #3fb950;
    --orange: #f0883e;
    --purple: #a371f7;
    --yellow: #d29922;
    --red: #f85149;
    --shadow: 0 1px 3px rgba(0,0,0,0.3), 0 1px 2px rgba(0,0,0,0.2);
    --shadow-lg: 0 4px 12px rgba(0,0,0,0.4);
    --radius: 8px;
    --radius-sm: 6px;
    --max-width: 960px;
    --transition: 0.2s ease;
}

/* ===== Reset & Base ===== */
*, *::before, *::after {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}

html {
    scroll-behavior: smooth;
    -webkit-text-size-adjust: 100%;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "Noto Sans", Helvetica, Arial, sans-serif;
    background: var(--bg-primary);
    color: var(--text-primary);
    line-height: 1.6;
    min-height: 100vh;
}

a {
    color: var(--accent);
    text-decoration: none;
    transition: color var(--transition);
}

a:hover {
    color: var(--accent-hover);
}

/* ===== Header ===== */
.header {
    background: var(--bg-secondary);
    border-bottom: 1px solid var(--border);
    position: sticky;
    top: 0;
    z-index: 100;
    backdrop-filter: blur(12px);
    background: rgba(22, 27, 34, 0.95);
}

.header-inner {
    max-width: var(--max-width);
    margin: 0 auto;
    padding: 16px 20px 12px;
}

.header-top {
    display: flex;
    align-items: center;
    justify-content: space-between;
    margin-bottom: 12px;
}

.logo {
    font-size: 18px;
    font-weight: 700;
    color: var(--text-primary);
    display: flex;
    align-items: center;
    gap: 8px;
}

.logo-icon {
    font-size: 24px;
}

.github-link {
    color: var(--text-secondary);
    transition: color var(--transition);
    display: flex;
    align-items: center;
}

.github-link:hover {
    color: var(--text-primary);
}

/* Search */
.search-bar {
    margin-bottom: 12px;
}

.search-wrapper {
    position: relative;
    display: flex;
    align-items: center;
}

.search-icon {
    position: absolute;
    left: 12px;
    color: var(--text-tertiary);
    pointer-events: none;
}

#searchInput {
    width: 100%;
    padding: 10px 44px 10px 40px;
    background: var(--bg-primary);
    border: 1px solid var(--border);
    border-radius: var(--radius);
    color: var(--text-primary);
    font-size: 14px;
    outline: none;
    transition: border-color var(--transition), box-shadow var(--transition);
}

#searchInput:focus {
    border-color: var(--accent);
    box-shadow: 0 0 0 3px rgba(88, 166, 255, 0.15);
}

#searchInput::placeholder {
    color: var(--text-tertiary);
}

.search-kbd {
    position: absolute;
    right: 10px;
    padding: 2px 8px;
    font-size: 12px;
    font-family: monospace;
    background: var(--bg-tertiary);
    border: 1px solid var(--border);
    border-radius: 4px;
    color: var(--text-tertiary);
    pointer-events: none;
}

/* Stats */
.stats-bar {
    display: flex;
    gap: 20px;
}

.stat-item {
    display: flex;
    align-items: center;
    gap: 4px;
    font-size: 13px;
}

.stat-number {
    font-weight: 700;
    color: var(--text-primary);
    font-variant-numeric: tabular-nums;
}

.stat-label {
    color: var(--text-secondary);
}

.stat-item.featured .stat-number {
    color: var(--yellow);
}

/* ===== Filters (Level 1) ===== */
.filters {
    background: var(--bg-secondary);
    border-bottom: 1px solid var(--border);
    position: sticky;
    top: 0;
    z-index: 99;
}

.filters-inner {
    max-width: var(--max-width);
    margin: 0 auto;
    padding: 10px 20px;
    display: flex;
    justify-content: space-between;
    align-items: center;
    gap: 12px;
    flex-wrap: wrap;
}

.category-tabs {
    display: flex;
    gap: 4px;
    overflow-x: auto;
    -webkit-overflow-scrolling: touch;
    scrollbar-width: none;
    flex: 1;
    min-width: 0;
}

.category-tabs::-webkit-scrollbar {
    display: none;
}

.cat-btn {
    display: flex;
    align-items: center;
    gap: 4px;
    padding: 6px 12px;
    border: 1px solid transparent;
    border-radius: 20px;
    background: transparent;
    color: var(--text-secondary);
    font-size: 13px;
    cursor: pointer;
    white-space: nowrap;
    transition: all var(--transition);
    flex-shrink: 0;
}

.cat-btn:hover {
    background: var(--bg-tertiary);
    color: var(--text-primary);
}

.cat-btn.active {
    background: var(--accent);
    color: #fff;
    border-color: var(--accent);
}

.cat-icon {
    font-size: 14px;
}

.cat-count {
    font-size: 11px;
    padding: 0 6px;
    border-radius: 10px;
    background: rgba(255,255,255,0.1);
    font-weight: 600;
}

.cat-btn.active .cat-count {
    background: rgba(255,255,255,0.25);
}

.time-filter {
    display: flex;
    align-items: center;
    gap: 8px;
    flex-shrink: 0;
}

#monthFilter {
    padding: 6px 28px 6px 10px;
    background: var(--bg-primary);
    border: 1px solid var(--border);
    border-radius: var(--radius-sm);
    color: var(--text-primary);
    font-size: 13px;
    cursor: pointer;
    outline: none;
    appearance: none;
    background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='12' height='12' viewBox='0 0 24 24' fill='none' stroke='%238b949e' stroke-width='2'%3E%3Cpath d='m6 9 6 6 6-6'/%3E%3C/svg%3E");
    background-repeat: no-repeat;
    background-position: right 8px center;
}

#monthFilter:focus {
    border-color: var(--accent);
}

.sort-toggle {
    display: flex;
    border: 1px solid var(--border);
    border-radius: var(--radius-sm);
    overflow: hidden;
}

.sort-btn {
    padding: 5px 10px;
    background: transparent;
    border: none;
    color: var(--text-secondary);
    font-size: 12px;
    cursor: pointer;
    transition: all var(--transition);
    white-space: nowrap;
}

.sort-btn:hover {
    background: var(--bg-tertiary);
}

.sort-btn.active {
    background: var(--bg-tertiary);
    color: var(--text-primary);
}

/* ===== Subcategory Filters (Level 2) ===== */
.subfilters {
    background: var(--bg-primary);
    border-bottom: 1px solid var(--border);
    position: sticky;
    top: 0;
    z-index: 98;
}

.subfilters-inner {
    max-width: var(--max-width);
    margin: 0 auto;
    padding: 8px 20px;
}

.subcat-tabs {
    display: flex;
    gap: 6px;
    overflow-x: auto;
    -webkit-overflow-scrolling: touch;
    scrollbar-width: none;
    align-items: center;
}

.subcat-tabs::-webkit-scrollbar {
    display: none;
}

.subcat-label {
    font-size: 12px;
    color: var(--text-tertiary);
    margin-right: 4px;
    flex-shrink: 0;
    white-space: nowrap;
}

.subcat-btn {
    display: inline-flex;
    align-items: center;
    gap: 3px;
    padding: 4px 10px;
    border: 1px solid var(--border);
    border-radius: 14px;
    background: transparent;
    color: var(--text-secondary);
    font-size: 12px;
    cursor: pointer;
    white-space: nowrap;
    transition: all var(--transition);
    flex-shrink: 0;
}

.subcat-btn:hover {
    background: var(--bg-tertiary);
    color: var(--text-primary);
    border-color: #40464e;
}

.subcat-btn.active {
    color: #fff;
    border-color: transparent;
}

.subcat-btn .subcat-count {
    font-size: 10px;
    padding: 0 5px;
    border-radius: 8px;
    background: rgba(255,255,255,0.08);
    font-weight: 600;
}

.subcat-btn.active .subcat-count {
    background: rgba(255,255,255,0.25);
}

/* ===== Main ===== */
.main {
    max-width: var(--max-width);
    margin: 0 auto;
    padding: 16px 20px 60px;
}

/* ===== Issue Cards ===== */
.issue-list {
    display: flex;
    flex-direction: column;
    gap: 8px;
}

.issue-card {
    background: var(--bg-card);
    border: 1px solid var(--border);
    border-radius: var(--radius);
    padding: 16px;
    transition: all var(--transition);
    cursor: default;
}

.issue-card:hover {
    background: var(--bg-card-hover);
    border-color: #40464e;
}

.issue-card.featured {
    border-left: 3px solid var(--yellow);
}

.card-header {
    display: flex;
    align-items: flex-start;
    gap: 10px;
    margin-bottom: 8px;
}

.card-number {
    font-size: 12px;
    color: var(--text-tertiary);
    font-weight: 600;
    padding-top: 2px;
    flex-shrink: 0;
}

.card-title-area {
    flex: 1;
    min-width: 0;
}

.card-title {
    font-size: 15px;
    font-weight: 600;
    line-height: 1.4;
    word-break: break-word;
}

.card-title a {
    color: var(--text-primary);
}

.card-title a:hover {
    color: var(--accent);
}

.featured-badge {
    display: inline-flex;
    align-items: center;
    gap: 2px;
    font-size: 11px;
    color: var(--yellow);
    margin-left: 6px;
    vertical-align: middle;
}

.card-meta {
    display: flex;
    align-items: center;
    gap: 8px;
    margin-top: 6px;
    flex-wrap: wrap;
}

.card-category {
    display: inline-block;
    padding: 2px 8px;
    border-radius: 12px;
    font-size: 11px;
    font-weight: 600;
    line-height: 1.5;
    white-space: nowrap;
}

.card-subcategory {
    display: inline-block;
    padding: 2px 7px;
    border-radius: 10px;
    font-size: 10px;
    font-weight: 600;
    line-height: 1.5;
    white-space: nowrap;
    border: 1px solid;
}

.card-author {
    display: flex;
    align-items: center;
    gap: 4px;
    font-size: 12px;
    color: var(--text-secondary);
}

.card-avatar {
    width: 18px;
    height: 18px;
    border-radius: 50%;
    flex-shrink: 0;
}

.card-time {
    font-size: 12px;
    color: var(--text-tertiary);
}

.card-body {
    margin-top: 8px;
    font-size: 13px;
    color: var(--text-secondary);
    line-height: 1.6;
    overflow: hidden;
    position: relative;
}

.card-body.collapsed {
    max-height: 3.2em;
}

.card-body.collapsed::after {
    content: '';
    position: absolute;
    bottom: 0;
    left: 0;
    right: 0;
    height: 1.6em;
    background: linear-gradient(transparent, var(--bg-card));
    pointer-events: none;
}

.issue-card:hover .card-body.collapsed::after {
    background: linear-gradient(transparent, var(--bg-card-hover));
}

.expand-btn {
    display: inline-block;
    margin-top: 4px;
    font-size: 12px;
    color: var(--accent);
    cursor: pointer;
    background: none;
    border: none;
    padding: 0;
}

.expand-btn:hover {
    color: var(--accent-hover);
}

.card-footer {
    display: flex;
    align-items: center;
    gap: 14px;
    margin-top: 10px;
    padding-top: 8px;
    border-top: 1px solid var(--border-light);
}

.card-stat {
    display: flex;
    align-items: center;
    gap: 3px;
    font-size: 12px;
    color: var(--text-tertiary);
}

.card-stat svg {
    width: 14px;
    height: 14px;
}

/* ===== Loading ===== */
.loading {
    text-align: center;
    padding: 40px;
    color: var(--text-secondary);
}

.loading-spinner {
    width: 32px;
    height: 32px;
    border: 3px solid var(--border);
    border-top-color: var(--accent);
    border-radius: 50%;
    animation: spin 0.8s linear infinite;
    margin: 0 auto 12px;
}

@keyframes spin {
    to { transform: rotate(360deg); }
}

/* ===== Empty State ===== */
.empty-state {
    text-align: center;
    padding: 60px 20px;
    color: var(--text-secondary);
}

.empty-icon {
    font-size: 48px;
    margin-bottom: 12px;
}

.reset-btn {
    margin-top: 16px;
    padding: 8px 20px;
    background: var(--accent);
    color: #fff;
    border: none;
    border-radius: var(--radius-sm);
    font-size: 14px;
    cursor: pointer;
    transition: background var(--transition);
}

.reset-btn:hover {
    background: var(--accent-hover);
}

/* ===== Back to Top ===== */
.back-to-top {
    position: fixed;
    bottom: 24px;
    right: 24px;
    width: 40px;
    height: 40px;
    background: var(--bg-tertiary);
    border: 1px solid var(--border);
    border-radius: 50%;
    color: var(--text-secondary);
    font-size: 18px;
    cursor: pointer;
    display: none;
    align-items: center;
    justify-content: center;
    transition: all var(--transition);
    z-index: 50;
}

.back-to-top:hover {
    background: var(--accent);
    color: #fff;
    border-color: var(--accent);
}

.back-to-top.visible {
    display: flex;
}

/* ===== Footer ===== */
.footer {
    text-align: center;
    padding: 20px;
    font-size: 13px;
    color: var(--text-tertiary);
    border-top: 1px solid var(--border);
}

/* ===== Responsive ===== */
@media (max-width: 768px) {
    .header-inner {
        padding: 12px 16px 10px;
    }

    .logo {
        font-size: 15px;
    }

    .logo-icon {
        font-size: 20px;
    }

    .stats-bar {
        gap: 14px;
    }

    .stat-item {
        font-size: 12px;
    }

    .filters-inner {
        padding: 8px 16px;
        flex-direction: column;
        align-items: stretch;
    }

    .category-tabs {
        padding-bottom: 4px;
    }

    .cat-btn {
        padding: 5px 10px;
        font-size: 12px;
    }

    .time-filter {
        justify-content: space-between;
    }

    .subfilters-inner {
        padding: 6px 16px;
    }

    .subcat-btn {
        font-size: 11px;
        padding: 3px 8px;
    }

    .main {
        padding: 12px 16px 60px;
    }

    .issue-card {
        padding: 12px;
    }

    .card-title {
        font-size: 14px;
    }

    .card-meta {
        gap: 6px;
    }

    .card-footer {
        gap: 10px;
    }

    .back-to-top {
        bottom: 16px;
        right: 16px;
    }

    .search-kbd {
        display: none;
    }
}

@media (max-width: 480px) {
    .stats-bar {
        gap: 10px;
        flex-wrap: wrap;
    }

    .card-header {
        flex-direction: column;
        gap: 4px;
    }

    .card-number {
        font-size: 11px;
    }
}

/* ===== Scrollbar ===== */
::-webkit-scrollbar {
    width: 8px;
}

::-webkit-scrollbar-track {
    background: var(--bg-primary);
}

::-webkit-scrollbar-thumb {
    background: var(--bg-tertiary);
    border-radius: 4px;
}

::-webkit-scrollbar-thumb:hover {
    background: var(--border);
}

/* ===== Selection ===== */
::selection {
    background: rgba(88, 166, 255, 0.3);
}