/* ============================================================
   CPTBHH — Design System
   Competitive Programming Teaching Platform
   Dark-first, tech-modern aesthetic
   ============================================================ */

/* ============================================================
   IMPORTS
   ============================================================ */
@import url('https://fonts.googleapis.com/css2?family=Inter:wght@300;400;500;600;700;800&family=JetBrains+Mono:wght@400;500;600&display=swap');

/* ============================================================
   CSS VARIABLES — DARK THEME (DEFAULT)
   ============================================================ */
:root {
    /* === Colors === */
    --bg-primary: #0a0e17;
    --bg-secondary: #111827;
    --bg-tertiary: #1a2332;
    --bg-card: #151d2e;
    --bg-hover: #1e293b;
    --bg-input: #1a2332;
    --bg-overlay: rgba(0, 0, 0, 0.6);

    --text-primary: #e2e8f0;
    --text-secondary: #94a3b8;
    --text-muted: #64748b;
    --text-inverse: #0f172a;

    --border-color: #1e293b;
    --border-hover: #334155;
    --border-focus: #6366f1;

    /* === Accent Colors === */
    --accent-primary: #6366f1;
    --accent-primary-hover: #818cf8;
    --accent-primary-glow: rgba(99, 102, 241, 0.3);
    --accent-secondary: #06b6d4;
    --accent-success: #10b981;
    --accent-warning: #f59e0b;
    --accent-danger: #ef4444;
    --accent-info: #3b82f6;

    /* === Gradient === */
    --gradient-primary: linear-gradient(135deg, #6366f1 0%, #8b5cf6 50%, #06b6d4 100%);
    --gradient-card: linear-gradient(145deg, #151d2e 0%, #111827 100%);
    --gradient-sidebar: linear-gradient(180deg, #0d1321 0%, #111827 100%);
    --gradient-header: linear-gradient(90deg, rgba(10, 14, 23, 0.95) 0%, rgba(17, 24, 39, 0.95) 100%);

    /* === Difficulty Colors === */
    --difficulty-easy: #10b981;
    --difficulty-medium: #f59e0b;
    --difficulty-hard: #ef4444;

    /* === Typography === */
    --font-family: 'Inter', -apple-system, BlinkMacSystemFont, sans-serif;
    --font-mono: 'JetBrains Mono', 'Fira Code', monospace;
    --font-size-xs: 0.75rem;
    --font-size-sm: 0.875rem;
    --font-size-base: 1rem;
    --font-size-lg: 1.125rem;
    --font-size-xl: 1.25rem;
    --font-size-2xl: 1.5rem;
    --font-size-3xl: 1.875rem;
    --font-size-4xl: 2.25rem;

    /* === Spacing === */
    --spacing-xs: 0.25rem;
    --spacing-sm: 0.5rem;
    --spacing-md: 1rem;
    --spacing-lg: 1.5rem;
    --spacing-xl: 2rem;
    --spacing-2xl: 3rem;

    /* === Border Radius === */
    --radius-sm: 6px;
    --radius-md: 10px;
    --radius-lg: 16px;
    --radius-xl: 24px;
    --radius-full: 9999px;

    /* === Shadows === */
    --shadow-sm: 0 1px 3px rgba(0, 0, 0, 0.3);
    --shadow-md: 0 4px 12px rgba(0, 0, 0, 0.4);
    --shadow-lg: 0 8px 30px rgba(0, 0, 0, 0.5);
    --shadow-glow: 0 0 20px rgba(99, 102, 241, 0.15);

    /* === Transitions === */
    --transition-fast: 0.15s ease;
    --transition-normal: 0.25s ease;
    --transition-slow: 0.4s ease;

    /* === Layout === */
    --header-height: 64px;
    --sidebar-width: 280px;
    --sidebar-collapsed-width: 60px;
    --content-max-width: 1200px;

    /* === Glassmorphism === */
    --glass-bg: rgba(17, 24, 39, 0.7);
    --glass-border: rgba(255, 255, 255, 0.06);
    --glass-blur: 12px;
}

/* ============================================================
   LIGHT THEME
   ============================================================ */
[data-theme="light"] {
    --bg-primary: #f8fafc;
    --bg-secondary: #ffffff;
    --bg-tertiary: #f1f5f9;
    --bg-card: #ffffff;
    --bg-hover: #f1f5f9;
    --bg-input: #f8fafc;
    --bg-overlay: rgba(0, 0, 0, 0.3);

    --text-primary: #1e293b;
    --text-secondary: #475569;
    --text-muted: #94a3b8;
    --text-inverse: #f8fafc;

    --border-color: #e2e8f0;
    --border-hover: #cbd5e1;
    --border-focus: #6366f1;

    --gradient-card: linear-gradient(145deg, #ffffff 0%, #f8fafc 100%);
    --gradient-sidebar: linear-gradient(180deg, #f8fafc 0%, #ffffff 100%);
    --gradient-header: linear-gradient(90deg, rgba(248, 250, 252, 0.95) 0%, rgba(255, 255, 255, 0.95) 100%);

    --shadow-sm: 0 1px 3px rgba(0, 0, 0, 0.08);
    --shadow-md: 0 4px 12px rgba(0, 0, 0, 0.1);
    --shadow-lg: 0 8px 30px rgba(0, 0, 0, 0.12);
    --shadow-glow: 0 0 20px rgba(99, 102, 241, 0.1);

    --glass-bg: rgba(255, 255, 255, 0.7);
    --glass-border: rgba(0, 0, 0, 0.06);
}

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

html {
    scroll-behavior: smooth;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

body {
    font-family: var(--font-family);
    font-size: var(--font-size-base);
    line-height: 1.6;
    color: var(--text-primary);
    background-color: var(--bg-primary);
    min-height: 100vh;
    transition: background-color var(--transition-normal), color var(--transition-normal);
}

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

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

img {
    max-width: 100%;
    height: auto;
}

/* ============================================================
   SCROLLBAR
   ============================================================ */
::-webkit-scrollbar {
    width: 6px;
    height: 6px;
}

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

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

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

/* ============================================================
   LAYOUT
   ============================================================ */
.app-layout {
    display: flex;
    min-height: 100vh;
    padding-top: var(--header-height);
}

.app-main {
    flex: 1;
    padding: var(--spacing-xl);
    max-width: var(--content-max-width);
    margin: 0 auto;
    width: 100%;
}

.app-main.with-sidebar {
    margin-left: var(--sidebar-width);
}

/* ============================================================
   HEADER
   ============================================================ */
.app-header {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    height: var(--header-height);
    background: var(--gradient-header);
    backdrop-filter: blur(var(--glass-blur));
    -webkit-backdrop-filter: blur(var(--glass-blur));
    border-bottom: 1px solid var(--glass-border);
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 0 var(--spacing-xl);
    z-index: 1000;
    transition: background var(--transition-normal);
}

.header-logo {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
    font-size: var(--font-size-xl);
    font-weight: 700;
    color: var(--text-primary);
    text-decoration: none;
}

.header-logo .logo-icon {
    width: 36px;
    height: 36px;
    background: var(--gradient-primary);
    border-radius: var(--radius-md);
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.2rem;
    color: white;
    box-shadow: var(--shadow-glow);
}

.header-nav {
    display: flex;
    align-items: center;
    gap: var(--spacing-xs);
}

.header-nav a {
    display: flex;
    align-items: center;
    gap: var(--spacing-xs);
    padding: var(--spacing-sm) var(--spacing-md);
    color: var(--text-secondary);
    border-radius: var(--radius-md);
    font-size: var(--font-size-sm);
    font-weight: 500;
    transition: all var(--transition-fast);
    text-decoration: none;
    position: relative;
}

.header-nav a:hover,
.header-nav a.active {
    color: var(--accent-primary);
    background: var(--accent-primary-glow);
}

.header-nav a.active::after {
    content: '';
    position: absolute;
    bottom: -1px;
    left: 50%;
    transform: translateX(-50%);
    width: 20px;
    height: 2px;
    background: var(--accent-primary);
    border-radius: var(--radius-full);
}

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

.header-user-info {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
    padding: var(--spacing-xs) var(--spacing-sm);
    border-radius: var(--radius-md);
    cursor: pointer;
    transition: background var(--transition-fast);
    position: relative;
}

.header-user-info:hover {
    background: var(--bg-hover);
}

.user-avatar {
    width: 36px;
    height: 36px;
    border-radius: var(--radius-full);
    object-fit: cover;
    border: 2px solid var(--border-color);
    transition: border-color var(--transition-fast);
}

.user-avatar.placeholder {
    background: var(--gradient-primary);
    display: flex;
    align-items: center;
    justify-content: center;
    color: white;
    font-weight: 600;
    font-size: var(--font-size-sm);
}

.header-user-info:hover .user-avatar {
    border-color: var(--accent-primary);
}

.user-name {
    font-size: var(--font-size-sm);
    font-weight: 500;
    color: var(--text-primary);
}

.user-role {
    font-size: var(--font-size-xs);
    color: var(--text-muted);
}

/* User dropdown */
.user-dropdown {
    position: absolute;
    top: calc(100% + 8px);
    right: 0;
    background: var(--bg-card);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    box-shadow: var(--shadow-lg);
    min-width: 200px;
    opacity: 0;
    visibility: hidden;
    transform: translateY(-8px);
    transition: all var(--transition-fast);
    z-index: 1001;
    overflow: hidden;
}

.user-dropdown.show {
    opacity: 1;
    visibility: visible;
    transform: translateY(0);
}

.user-dropdown a,
.user-dropdown button {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
    width: 100%;
    padding: var(--spacing-sm) var(--spacing-md);
    color: var(--text-secondary);
    font-size: var(--font-size-sm);
    border: none;
    background: none;
    cursor: pointer;
    transition: all var(--transition-fast);
    text-align: left;
    font-family: var(--font-family);
}

.user-dropdown a:hover,
.user-dropdown button:hover {
    background: var(--bg-hover);
    color: var(--text-primary);
}

.user-dropdown .dropdown-divider {
    height: 1px;
    background: var(--border-color);
    margin: var(--spacing-xs) 0;
}

.user-dropdown .logout-btn {
    color: var(--accent-danger);
}

.user-dropdown .logout-btn:hover {
    background: rgba(239, 68, 68, 0.1);
}

/* ============================================================
   SIDEBAR
   ============================================================ */
.app-sidebar {
    position: fixed;
    top: var(--header-height);
    left: 0;
    bottom: 0;
    width: var(--sidebar-width);
    background: var(--gradient-sidebar);
    border-right: 1px solid var(--border-color);
    overflow-y: auto;
    overflow-x: hidden;
    padding: var(--spacing-md) 0;
    z-index: 900;
    transition: transform var(--transition-normal), width var(--transition-normal);
}

.sidebar-section {
    margin-bottom: var(--spacing-sm);
}

.sidebar-section-title {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: var(--spacing-sm) var(--spacing-md);
    font-size: var(--font-size-xs);
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.05em;
    color: var(--text-muted);
    cursor: pointer;
    user-select: none;
    transition: color var(--transition-fast);
}

.sidebar-section-title:hover {
    color: var(--text-secondary);
}

.sidebar-section-title .chevron {
    font-size: 0.6rem;
    transition: transform var(--transition-fast);
}

.sidebar-section.collapsed .chevron {
    transform: rotate(-90deg);
}

.sidebar-section.collapsed .sidebar-section-items {
    display: none;
}

.sidebar-item {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
    padding: 8px var(--spacing-md) 8px calc(var(--spacing-md) + 12px);
    color: var(--text-secondary);
    font-size: var(--font-size-sm);
    text-decoration: none;
    transition: all var(--transition-fast);
    border-left: 3px solid transparent;
    cursor: pointer;
}

.sidebar-item:hover {
    color: var(--text-primary);
    background: var(--bg-hover);
    border-left-color: var(--border-hover);
}

.sidebar-item.active {
    color: var(--accent-primary);
    background: var(--accent-primary-glow);
    border-left-color: var(--accent-primary);
    font-weight: 500;
}

.sidebar-item .item-icon {
    font-size: var(--font-size-sm);
    opacity: 0.7;
    width: 20px;
    text-align: center;
}

/* ============================================================
   BUTTONS
   ============================================================ */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: var(--spacing-sm);
    padding: 10px 20px;
    font-family: var(--font-family);
    font-size: var(--font-size-sm);
    font-weight: 500;
    border: 1px solid transparent;
    border-radius: var(--radius-md);
    cursor: pointer;
    transition: all var(--transition-fast);
    text-decoration: none;
    line-height: 1.4;
    white-space: nowrap;
}

.btn:active {
    transform: scale(0.97);
}

.btn-primary {
    background: var(--accent-primary);
    color: white;
    box-shadow: 0 2px 8px var(--accent-primary-glow);
}

.btn-primary:hover {
    background: var(--accent-primary-hover);
    box-shadow: 0 4px 16px var(--accent-primary-glow);
    color: white;
}

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

.btn-secondary:hover {
    background: var(--bg-hover);
    border-color: var(--border-hover);
}

.btn-danger {
    background: var(--accent-danger);
    color: white;
}

.btn-danger:hover {
    background: #dc2626;
}

.btn-ghost {
    background: transparent;
    color: var(--text-secondary);
}

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

.btn-sm {
    padding: 6px 12px;
    font-size: var(--font-size-xs);
}

.btn-lg {
    padding: 14px 28px;
    font-size: var(--font-size-base);
}

.btn-icon {
    width: 36px;
    height: 36px;
    padding: 0;
    border-radius: var(--radius-md);
}

.btn-block {
    width: 100%;
}

/* ============================================================
   FORMS
   ============================================================ */
.form-group {
    margin-bottom: var(--spacing-lg);
}

.form-label {
    display: block;
    margin-bottom: var(--spacing-sm);
    font-size: var(--font-size-sm);
    font-weight: 500;
    color: var(--text-secondary);
}

.form-input,
.form-select,
.form-textarea {
    width: 100%;
    padding: 10px 14px;
    font-family: var(--font-family);
    font-size: var(--font-size-sm);
    color: var(--text-primary);
    background: var(--bg-input);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    outline: none;
    transition: all var(--transition-fast);
}

.form-input:focus,
.form-select:focus,
.form-textarea:focus {
    border-color: var(--border-focus);
    box-shadow: 0 0 0 3px var(--accent-primary-glow);
}

.form-input::placeholder {
    color: var(--text-muted);
}

.form-textarea {
    resize: vertical;
    min-height: 100px;
}

.form-select {
    cursor: pointer;
    appearance: none;
    background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='12' height='12' viewBox='0 0 12 12'%3E%3Cpath fill='%2394a3b8' d='M6 8L1 3h10z'/%3E%3C/svg%3E");
    background-repeat: no-repeat;
    background-position: right 12px center;
    padding-right: 36px;
}

.form-select option {
    background: var(--bg-secondary);
    color: var(--text-primary);
}

.form-hint {
    margin-top: var(--spacing-xs);
    font-size: var(--font-size-xs);
    color: var(--text-muted);
}

.form-error {
    color: var(--accent-danger);
}

/* ============================================================
   CARDS
   ============================================================ */
.card {
    background: var(--gradient-card);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-lg);
    padding: var(--spacing-xl);
    transition: all var(--transition-normal);
    position: relative;
    overflow: hidden;
}

.card::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    height: 1px;
    background: linear-gradient(90deg, transparent, var(--glass-border), transparent);
}

.card:hover {
    border-color: var(--border-hover);
    box-shadow: var(--shadow-md);
}

.card-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    margin-bottom: var(--spacing-lg);
}

.card-title {
    font-size: var(--font-size-lg);
    font-weight: 600;
    color: var(--text-primary);
}

/* ============================================================
   BADGES
   ============================================================ */
.badge {
    display: inline-flex;
    align-items: center;
    padding: 2px 10px;
    font-size: var(--font-size-xs);
    font-weight: 600;
    border-radius: var(--radius-full);
    letter-spacing: 0.02em;
}

.badge-easy {
    background: rgba(16, 185, 129, 0.15);
    color: var(--difficulty-easy);
}

.badge-medium {
    background: rgba(245, 158, 11, 0.15);
    color: var(--difficulty-medium);
}

.badge-hard {
    background: rgba(239, 68, 68, 0.15);
    color: var(--difficulty-hard);
}

.badge-primary {
    background: var(--accent-primary-glow);
    color: var(--accent-primary);
}

.badge-category {
    background: rgba(6, 182, 212, 0.15);
    color: var(--accent-secondary);
}

/* ============================================================
   TABS
   ============================================================ */
.tabs {
    display: flex;
    gap: 2px;
    border-bottom: 1px solid var(--border-color);
    margin-bottom: var(--spacing-xl);
}

.tab {
    padding: var(--spacing-sm) var(--spacing-lg);
    font-size: var(--font-size-sm);
    font-weight: 500;
    color: var(--text-muted);
    cursor: pointer;
    border-bottom: 2px solid transparent;
    transition: all var(--transition-fast);
    background: none;
    border-top: none;
    border-left: none;
    border-right: none;
    font-family: var(--font-family);
}

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

.tab.active {
    color: var(--accent-primary);
    border-bottom-color: var(--accent-primary);
}

.tab-content {
    display: none;
}

.tab-content.active {
    display: block;
    animation: fadeIn 0.25s ease;
}

/* ============================================================
   TABLE
   ============================================================ */
.data-table {
    width: 100%;
    border-collapse: collapse;
}

.data-table th,
.data-table td {
    padding: 12px 16px;
    text-align: left;
    border-bottom: 1px solid var(--border-color);
    font-size: var(--font-size-sm);
}

.data-table th {
    font-weight: 600;
    color: var(--text-muted);
    font-size: var(--font-size-xs);
    text-transform: uppercase;
    letter-spacing: 0.05em;
    background: var(--bg-tertiary);
}

.data-table tr {
    transition: background var(--transition-fast);
}

.data-table tbody tr:hover {
    background: var(--bg-hover);
}

/* ============================================================
   MODAL
   ============================================================ */
.modal-overlay {
    position: fixed;
    inset: 0;
    background: var(--bg-overlay);
    backdrop-filter: blur(4px);
    display: flex;
    align-items: center;
    justify-content: center;
    z-index: 2000;
    opacity: 0;
    visibility: hidden;
    transition: all var(--transition-fast);
}

.modal-overlay.show {
    opacity: 1;
    visibility: visible;
}

.modal {
    background: var(--bg-card);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-lg);
    width: 90%;
    max-width: 560px;
    max-height: 90vh;
    overflow-y: auto;
    transform: scale(0.95) translateY(10px);
    transition: transform var(--transition-fast);
}

.modal-overlay.show .modal {
    transform: scale(1) translateY(0);
}

.modal-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: var(--spacing-lg) var(--spacing-xl);
    border-bottom: 1px solid var(--border-color);
}

.modal-title {
    font-size: var(--font-size-lg);
    font-weight: 600;
}

.modal-close {
    width: 32px;
    height: 32px;
    display: flex;
    align-items: center;
    justify-content: center;
    border: none;
    background: none;
    color: var(--text-muted);
    cursor: pointer;
    border-radius: var(--radius-sm);
    font-size: 1.2rem;
    transition: all var(--transition-fast);
}

.modal-close:hover {
    background: var(--bg-hover);
    color: var(--text-primary);
}

.modal-body {
    padding: var(--spacing-xl);
}

.modal-footer {
    display: flex;
    justify-content: flex-end;
    gap: var(--spacing-sm);
    padding: var(--spacing-lg) var(--spacing-xl);
    border-top: 1px solid var(--border-color);
}

/* ============================================================
   TOAST / NOTIFICATION
   ============================================================ */
.toast-container {
    position: fixed;
    top: calc(var(--header-height) + 16px);
    right: 16px;
    z-index: 3000;
    display: flex;
    flex-direction: column;
    gap: var(--spacing-sm);
}

.toast {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
    padding: 12px 20px;
    background: var(--bg-card);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    box-shadow: var(--shadow-lg);
    font-size: var(--font-size-sm);
    color: var(--text-primary);
    animation: slideInRight 0.3s ease, fadeOut 0.3s ease 2.7s forwards;
    max-width: 400px;
}

.toast.toast-success {
    border-left: 3px solid var(--accent-success);
}

.toast.toast-error {
    border-left: 3px solid var(--accent-danger);
}

.toast.toast-warning {
    border-left: 3px solid var(--accent-warning);
}

/* ============================================================
   CODE BLOCK
   ============================================================ */
.code-block {
    background: var(--bg-primary);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    overflow: hidden;
}

.code-block-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: var(--spacing-sm) var(--spacing-md);
    background: var(--bg-tertiary);
    border-bottom: 1px solid var(--border-color);
    font-size: var(--font-size-xs);
    color: var(--text-muted);
}

.code-block pre {
    padding: var(--spacing-md);
    overflow-x: auto;
    font-family: var(--font-mono);
    font-size: var(--font-size-sm);
    line-height: 1.7;
    color: var(--text-primary);
    margin: 0;
}

.code-editor {
    width: 100%;
    min-height: 300px;
    padding: var(--spacing-md);
    font-family: var(--font-mono);
    font-size: var(--font-size-sm);
    line-height: 1.7;
    color: var(--text-primary);
    background: var(--bg-primary);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    outline: none;
    resize: vertical;
    tab-size: 4;
    transition: border-color var(--transition-fast);
}

.code-editor:focus {
    border-color: var(--border-focus);
    box-shadow: 0 0 0 3px var(--accent-primary-glow);
}

/* ============================================================
   MESSAGE BUBBLE
   ============================================================ */
.message {
    display: flex;
    gap: var(--spacing-sm);
    padding: var(--spacing-sm) var(--spacing-md);
    transition: background var(--transition-fast);
}

.message:hover {
    background: var(--bg-hover);
}

.message-avatar {
    width: 36px;
    height: 36px;
    border-radius: var(--radius-full);
    flex-shrink: 0;
    object-fit: cover;
}

.message-body {
    flex: 1;
    min-width: 0;
}

.message-author {
    font-size: var(--font-size-sm);
    font-weight: 600;
    color: var(--accent-primary);
    margin-bottom: 2px;
}

.message-content {
    font-size: var(--font-size-sm);
    color: var(--text-primary);
    line-height: 1.6;
    word-wrap: break-word;
}

.message-content code {
    background: var(--bg-tertiary);
    padding: 1px 6px;
    border-radius: var(--radius-sm);
    font-family: var(--font-mono);
    font-size: 0.85em;
}

.message-content pre code {
    display: block;
    padding: var(--spacing-md);
    overflow-x: auto;
}

.message-time {
    font-size: var(--font-size-xs);
    color: var(--text-muted);
    margin-top: 4px;
}

.message-image {
    max-width: 400px;
    border-radius: var(--radius-md);
    margin-top: var(--spacing-sm);
    cursor: pointer;
    transition: opacity var(--transition-fast);
}

.message-image:hover {
    opacity: 0.9;
}

/* ============================================================
   LOGIN PAGE
   ============================================================ */
.login-container {
    display: flex;
    align-items: center;
    justify-content: center;
    min-height: 100vh;
    padding: var(--spacing-xl);
    background: var(--bg-primary);
    position: relative;
    overflow: hidden;
}

.login-container::before {
    content: '';
    position: absolute;
    top: -50%;
    left: -50%;
    width: 200%;
    height: 200%;
    background: radial-gradient(circle at 30% 50%, rgba(99, 102, 241, 0.08) 0%, transparent 50%),
                radial-gradient(circle at 70% 50%, rgba(6, 182, 212, 0.06) 0%, transparent 50%);
    animation: bgFloat 20s ease infinite;
}

.login-card {
    position: relative;
    background: var(--gradient-card);
    border: 1px solid var(--glass-border);
    border-radius: var(--radius-xl);
    padding: var(--spacing-2xl);
    width: 100%;
    max-width: 420px;
    box-shadow: var(--shadow-lg);
}

.login-card::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    height: 1px;
    background: linear-gradient(90deg, transparent, rgba(99, 102, 241, 0.3), transparent);
}

.login-logo {
    text-align: center;
    margin-bottom: var(--spacing-xl);
}

.login-logo .logo-icon {
    width: 56px;
    height: 56px;
    margin: 0 auto var(--spacing-md);
    background: var(--gradient-primary);
    border-radius: var(--radius-lg);
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.6rem;
    color: white;
    box-shadow: var(--shadow-glow);
}

.login-logo h1 {
    font-size: var(--font-size-2xl);
    font-weight: 700;
    background: var(--gradient-primary);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.login-logo p {
    font-size: var(--font-size-sm);
    color: var(--text-muted);
    margin-top: var(--spacing-xs);
}

/* ============================================================
   EMPTY STATE
   ============================================================ */
.empty-state {
    text-align: center;
    padding: var(--spacing-2xl);
    color: var(--text-muted);
}

.empty-state .empty-icon {
    font-size: 3rem;
    margin-bottom: var(--spacing-md);
    opacity: 0.5;
}

.empty-state h3 {
    font-size: var(--font-size-lg);
    color: var(--text-secondary);
    margin-bottom: var(--spacing-sm);
}

.empty-state p {
    font-size: var(--font-size-sm);
    max-width: 300px;
    margin: 0 auto;
}

/* ============================================================
   LOADING SPINNER
   ============================================================ */
.spinner {
    width: 24px;
    height: 24px;
    border: 3px solid var(--border-color);
    border-top-color: var(--accent-primary);
    border-radius: 50%;
    animation: spin 0.8s linear infinite;
}

.spinner-overlay {
    position: absolute;
    inset: 0;
    background: var(--bg-overlay);
    display: flex;
    align-items: center;
    justify-content: center;
    border-radius: inherit;
    z-index: 10;
}

/* ============================================================
   ANIMATIONS
   ============================================================ */
@keyframes fadeIn {
    from { opacity: 0; }
    to { opacity: 1; }
}

@keyframes fadeOut {
    from { opacity: 1; }
    to { opacity: 0; }
}

@keyframes slideInRight {
    from { transform: translateX(100%); opacity: 0; }
    to { transform: translateX(0); opacity: 1; }
}

@keyframes slideInUp {
    from { transform: translateY(20px); opacity: 0; }
    to { transform: translateY(0); opacity: 1; }
}

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

@keyframes bgFloat {
    0%, 100% { transform: translate(0, 0) rotate(0deg); }
    25% { transform: translate(2%, -2%) rotate(1deg); }
    50% { transform: translate(-1%, 3%) rotate(-0.5deg); }
    75% { transform: translate(1%, -1%) rotate(0.5deg); }
}

@keyframes pulse {
    0%, 100% { opacity: 1; }
    50% { opacity: 0.5; }
}

/* ============================================================
   PAGE TITLE
   ============================================================ */
.page-header {
    margin-bottom: var(--spacing-xl);
}

.page-title {
    font-size: var(--font-size-2xl);
    font-weight: 700;
    color: var(--text-primary);
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
}

.page-subtitle {
    font-size: var(--font-size-sm);
    color: var(--text-muted);
    margin-top: var(--spacing-xs);
}

/* ============================================================
   UTILITY CLASSES
   ============================================================ */
.text-center { text-align: center; }
.text-right { text-align: right; }
.text-muted { color: var(--text-muted); }
.text-success { color: var(--accent-success); }
.text-danger { color: var(--accent-danger); }
.text-warning { color: var(--accent-warning); }

.mt-sm { margin-top: var(--spacing-sm); }
.mt-md { margin-top: var(--spacing-md); }
.mt-lg { margin-top: var(--spacing-lg); }
.mb-sm { margin-bottom: var(--spacing-sm); }
.mb-md { margin-bottom: var(--spacing-md); }
.mb-lg { margin-bottom: var(--spacing-lg); }

.flex { display: flex; }
.flex-col { flex-direction: column; }
.items-center { align-items: center; }
.justify-between { justify-content: space-between; }
.gap-sm { gap: var(--spacing-sm); }
.gap-md { gap: var(--spacing-md); }

.hidden { display: none !important; }

/* ============================================================
   RESPONSIVE
   ============================================================ */
@media (max-width: 1024px) {
    .app-sidebar {
        transform: translateX(-100%);
    }

    .app-sidebar.open {
        transform: translateX(0);
    }

    .app-main.with-sidebar {
        margin-left: 0;
    }
}

@media (max-width: 768px) {
    :root {
        --spacing-xl: 1.25rem;
        --spacing-2xl: 2rem;
    }

    .app-header {
        padding: 0 var(--spacing-md);
    }

    .header-nav a span {
        display: none;
    }

    .login-card {
        padding: var(--spacing-xl);
    }

    .page-title {
        font-size: var(--font-size-xl);
    }
}