/* Shell-2 Desktop UI - Modern 3-Panel Layout */

/* ===== DESIGN TOKENS ===== */
:root {
    /* Colors */
    --bg-primary: #f8f9fa;
    --bg-secondary: #ffffff;
    --bg-tertiary: #f1f3f5;
    --text-primary: #1f2937;
    --text-secondary: #6b7280;
    --text-muted: #9ca3af;
    --accent-primary: #1e293b;
    --accent-hover: #475569;
    --border-light: #e5e7eb;
    --border-medium: #d1d5db;

    /* Spacing */
    --space-xs: 4px;
    --space-sm: 8px;
    --space-md: 16px;
    --space-lg: 24px;
    --space-xl: 32px;

    /* Typography */
    --font-sans: -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
    --font-mono: 'SF Mono', Monaco, monospace;
    --fs-xs: 10px;
    --fs-sm: 12px;
    --fs-md: 14px;
    --fs-lg: 16px;
    --fs-xl: 20px;
    --fw-normal: 400;
    --fw-medium: 500;
    --fw-bold: 700;
    --fw-black: 900;

    /* Radius */
    --radius-sm: 6px;
    --radius-md: 12px;
    --radius-lg: 16px;

    /* Shadow */
    --shadow-sm: 0 1px 3px rgba(0, 0, 0, 0.05);
    --shadow-md: 0 4px 12px rgba(0, 0, 0, 0.08);
}

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

body {
    font-family: var(--font-sans);
    background: var(--bg-primary);
    color: var(--text-primary);
    height: 100vh;
    display: flex;
    flex-direction: column;
    overflow: hidden;
}

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

::-webkit-scrollbar-track {
    background: transparent;
}

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

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

/* ===== HEADER ===== */
.app-header {
    height: 56px;
    background: var(--bg-secondary);
    border-bottom: 1px solid var(--border-light);
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 0 var(--space-lg);
    flex-shrink: 0;
}

.header-brand {
    display: flex;
    align-items: center;
    gap: var(--space-md);
}

.seal {
    font-size: 24px;
    width: 40px;
    height: 40px;
    display: flex;
    align-items: center;
    justify-content: center;
    background: var(--bg-tertiary);
    border-radius: var(--radius-sm);
}

.titles {
    display: flex;
    flex-direction: column;
    gap: 2px;
}

.main-title {
    font-size: var(--fs-lg);
    font-weight: var(--fw-black);
    text-transform: uppercase;
    letter-spacing: -0.5px;
    color: var(--text-primary);
}

.sub-title {
    font-size: var(--fs-xs);
    font-weight: var(--fw-bold);
    text-transform: uppercase;
    letter-spacing: 1.5px;
    color: var(--text-muted);
}

.search-trigger {
    display: flex;
    align-items: center;
    gap: var(--space-sm);
    padding: var(--space-sm) var(--space-md);
    background: var(--bg-tertiary);
    border: 1px solid var(--border-light);
    border-radius: var(--radius-sm);
    cursor: pointer;
    transition: all 0.2s;
}

.search-trigger:hover {
    background: var(--border-light);
}

.search-trigger .icon {
    font-size: var(--fs-md);
}

.search-trigger .label {
    font-size: var(--fs-xs);
    font-weight: var(--fw-black);
    text-transform: uppercase;
    letter-spacing: 1.5px;
}

/* ===== 3-PANEL LAYOUT ===== */
.explorer {
    flex: 1;
    display: flex;
    overflow: hidden;
}

.panel-left {
    width: 256px;
    background: var(--bg-secondary);
    border-right: 1px solid var(--border-light);
    display: flex;
    flex-direction: column;
    flex-shrink: 0;
}

.panel-middle {
    width: 400px;
    background: var(--bg-secondary);
    border-right: 1px solid var(--border-light);
    display: flex;
    flex-direction: column;
    flex-shrink: 0;
}

.panel-right {
    flex: 1;
    background: var(--bg-secondary);
    overflow: hidden;
}

/* ===== LEFT PANEL ===== */
.hierarchy-section,
.recent-section {
    padding: var(--space-lg);
}

.hierarchy-section {
    border-bottom: 1px solid var(--border-light);
}

.section-label {
    font-size: var(--fs-xs);
    font-weight: var(--fw-black);
    text-transform: uppercase;
    letter-spacing: 1.5px;
    color: var(--text-muted);
    margin-bottom: var(--space-md);
}

.level-nav {
    display: flex;
    flex-direction: column;
    gap: 4px;
}

.level-btn {
    width: 100%;
    padding: var(--space-sm) var(--space-md);
    background: transparent;
    border: 1px solid transparent;
    border-radius: var(--radius-sm);
    font-size: var(--fs-sm);
    font-weight: var(--fw-bold);
    text-transform: uppercase;
    letter-spacing: 1px;
    color: var(--text-secondary);
    cursor: pointer;
    transition: all 0.2s;
    text-align: left;
}

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

.level-btn.active {
    background: var(--accent-primary);
    color: white;
    border-color: var(--accent-primary);
}

.recent-list {
    display: flex;
    flex-direction: column;
    gap: var(--space-sm);
}

.recent-item {
    padding: var(--space-sm);
    background: var(--bg-tertiary);
    border: 1px solid transparent;
    border-radius: var(--radius-sm);
    cursor: pointer;
    transition: all 0.2s;
}

.recent-item:hover {
    border-color: var(--border-medium);
}

.recent-item-title {
    font-size: var(--fs-sm);
    font-weight: var(--fw-medium);
    color: var(--text-primary);
    margin-bottom: 4px;
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
}

.recent-item-level {
    font-size: var(--fs-xs);
    font-weight: var(--fw-black);
    text-transform: uppercase;
    letter-spacing: 0.5px;
    color: var(--text-muted);
}

/* ===== UTILITIES SECTION ===== */
.utilities-section {
    padding: var(--space-lg);
    border-top: 1px solid var(--border-light);
}

.utilities-nav {
    display: flex;
    flex-direction: column;
    gap: 4px;
}

.utility-link {
    padding: var(--space-sm) var(--space-md);
    background: transparent;
    border: 1px solid transparent;
    border-radius: var(--radius-sm);
    font-size: var(--fs-sm);
    font-weight: var(--fw-medium);
    color: var(--text-secondary);
    text-decoration: none;
    cursor: pointer;
    transition: all 0.2s;
    display: block;
}

.utility-link:hover {
    background: var(--bg-tertiary);
    color: var(--text-primary);
    border-color: var(--border-light);
}

/* ===== MIDDLE PANEL ===== */
.list-header {
    padding: var(--space-lg);
    border-bottom: 1px solid var(--border-light);
    display: flex;
    align-items: center;
    justify-content: space-between;
    flex-shrink: 0;
}

.list-title {
    display: flex;
    align-items: center;
    gap: var(--space-sm);
}

.level-badge {
    padding: 4px 8px;
    background: var(--bg-tertiary);
    border-radius: 4px;
    font-size: var(--fs-xs);
    font-weight: var(--fw-black);
    text-transform: uppercase;
    letter-spacing: 1px;
    color: var(--text-secondary);
}

#list-heading {
    font-size: var(--fs-lg);
    font-weight: var(--fw-black);
    text-transform: uppercase;
    letter-spacing: -0.5px;
}

.item-count {
    padding: 4px 12px;
    background: var(--bg-tertiary);
    border: 1px solid var(--border-light);
    border-radius: 12px;
    font-size: var(--fs-xs);
    font-weight: var(--fw-black);
    text-transform: uppercase;
    letter-spacing: 1px;
    color: var(--text-muted);
}

.search-bar {
    padding: var(--space-md) var(--space-lg);
    border-bottom: 1px solid var(--border-light);
    display: flex;
    gap: var(--space-sm);
    flex-shrink: 0;
}

.search-input {
    flex: 1;
    padding: var(--space-sm) var(--space-md);
    background: var(--bg-tertiary);
    border: 1px solid var(--border-light);
    border-radius: var(--radius-sm);
    font-size: var(--fs-sm);
    font-weight: var(--fw-medium);
    outline: none;
    transition: all 0.2s;
}

.search-input:focus {
    background: white;
    border-color: var(--accent-primary);
}

.clear-btn {
    padding: var(--space-sm) var(--space-md);
    background: transparent;
    border: 1px solid var(--border-light);
    border-radius: var(--radius-sm);
    font-size: var(--fs-xs);
    font-weight: var(--fw-black);
    text-transform: uppercase;
    letter-spacing: 1px;
    color: var(--text-secondary);
    cursor: pointer;
    transition: all 0.2s;
}

.clear-btn:hover {
    background: var(--bg-tertiary);
    border-color: var(--border-medium);
}

.clear-btn.hidden {
    display: none;
}

.item-list {
    flex: 1;
    overflow-y: auto;
    background: var(--bg-secondary);
}

.list-item {
    padding: var(--space-md) var(--space-lg);
    border-bottom: 1px solid var(--border-light);
    cursor: pointer;
    transition: all 0.2s;
    position: relative;
}

.list-item:hover {
    background: var(--bg-tertiary);
}

.list-item.active {
    background: rgba(30, 41, 59, 0.05);
}

.list-item.active::before {
    content: '';
    position: absolute;
    left: 0;
    top: 0;
    bottom: 0;
    width: 3px;
    background: var(--accent-primary);
}

.list-item-header {
    display: flex;
    align-items: flex-start;
    justify-content: space-between;
    margin-bottom: var(--space-sm);
}

.list-item-title {
    font-size: var(--fs-md);
    font-weight: var(--fw-bold);
    color: var(--text-primary);
    line-height: 1.4;
}

.list-item-meta {
    display: flex;
    align-items: center;
    gap: var(--space-sm);
    flex-wrap: wrap;
}

.meta-badge {
    padding: 2px 6px;
    background: var(--bg-tertiary);
    border-radius: 3px;
    font-size: var(--fs-xs);
    font-weight: var(--fw-black);
    text-transform: uppercase;
    letter-spacing: 0.5px;
    color: var(--text-muted);
}

.meta-path {
    font-size: var(--fs-xs);
    font-weight: var(--fw-medium);
    color: var(--text-muted);
    display: flex;
    align-items: center;
    gap: 4px;
}

/* ===== RIGHT PANEL (READER) ===== */
.reader-view {
    height: 100%;
    overflow-y: auto;
    padding: var(--space-xl);
}

.reader-header {
    margin-bottom: var(--space-xl);
    padding-bottom: var(--space-lg);
    border-bottom: 1px solid var(--border-light);
}

.reader-breadcrumb {
    display: flex;
    align-items: center;
    gap: 4px;
    margin-bottom: var(--space-md);
    font-size: var(--fs-xs);
    font-weight: var(--fw-black);
    text-transform: uppercase;
    letter-spacing: 1.5px;
    color: var(--text-muted);
}

.reader-title {
    font-size: 32px;
    font-weight: var(--fw-black);
    text-transform: uppercase;
    letter-spacing: -1px;
    line-height: 1.1;
    margin-bottom: var(--space-md);
}

.reader-meta {
    display: flex;
    align-items: center;
    gap: var(--space-lg);
    flex-wrap: wrap;
    font-size: var(--fs-sm);
    color: var(--text-secondary);
}

.reader-content {
    max-width: 720px;
    line-height: 1.7;
    font-size: var(--fs-lg);
    color: var(--text-primary);
}

.reader-content h1,
.reader-content h2,
.reader-content h3 {
    font-weight: var(--fw-black);
    text-transform: uppercase;
    letter-spacing: -0.5px;
    margin-top: var(--space-xl);
    margin-bottom: var(--space-md);
}

.reader-content h1 {
    font-size: 24px;
}

.reader-content h2 {
    font-size: 20px;
}

.reader-content h3 {
    font-size: 16px;
}

.reader-content p {
    margin-bottom: var(--space-md);
}

.reader-content blockquote {
    margin: var(--space-lg) 0;
    padding: var(--space-md);
    padding-left: var(--space-lg);
    background: var(--bg-tertiary);
    border-left: 3px solid var(--accent-primary);
    font-style: italic;
}

/* ===== READER NAVIGATION ===== */
.reader-nav {
    margin-top: var(--space-xl);
    padding-top: var(--space-lg);
    border-top: 1px solid var(--border-light);
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: var(--space-md);
}

.nav-btn {
    padding: var(--space-sm) var(--space-lg);
    background: var(--bg-secondary);
    border: 1px solid var(--border-medium);
    border-radius: var(--radius-sm);
    font-size: var(--fs-sm);
    font-weight: var(--fw-bold);
    text-transform: uppercase;
    letter-spacing: 0.5px;
    color: var(--text-primary);
    cursor: pointer;
    transition: all 0.2s;
}

.nav-btn:hover:not(:disabled) {
    background: var(--accent-primary);
    color: white;
    border-color: var(--accent-primary);
}

.nav-btn:disabled {
    opacity: 0.3;
    cursor: not-allowed;
}

.nav-btn-parent {
    background: var(--bg-tertiary);
}

/* ===== EMPTY STATES ===== */
.empty-state {
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    padding: var(--space-xl);
    text-align: center;
    color: var(--text-muted);
    min-height: 200px;
}

.empty-icon {
    font-size: 48px;
    margin-bottom: var(--space-md);
    opacity: 0.3;
}

.empty-state h3 {
    font-size: var(--fs-md);
    font-weight: var(--fw-black);
    text-transform: uppercase;
    letter-spacing: 1px;
    margin-bottom: var(--space-sm);
}

.empty-state p {
    font-size: var(--fs-sm);
    font-weight: var(--fw-medium);
}

/* ===== LOADING STATE ===== */
.loading-skeleton {
    padding: var(--space-md) var(space-lg);
    border-bottom: 1px solid var(--border-light);
}

.skeleton-line {
    height: 12px;
    background: var(--bg-tertiary);
    border-radius: 4px;
    margin-bottom: var(--space-sm);
    animation: pulse 1.5s infinite;
}

.skeleton-line:last-child {
    width: 60%;
}

@keyframes pulse {

    0%,
    100% {
        opacity: 1;
    }

    50% {
        opacity: 0.5;
    }
}