/* ====== CSS Variables ====== */
:root {
    --primary: #4f6ef7;
    --primary-hover: #3b5ce4;
    --primary-light: #eef1fe;
    --success: #34c759;
    --success-hover: #2aad4a;
    --danger: #ff3b30;
    --danger-hover: #e0332a;

    --bg: #f5f5f7;
    --sidebar-bg: #ffffff;
    --sidebar-width: 280px;
    --content-bg: #ffffff;
    --border: #e5e5ea;

    --text-primary: #1d1d1f;
    --text-secondary: #6e6e73;
    --text-tertiary: #aeaeb2;

    --radius: 8px;
    --radius-sm: 6px;
    --shadow-sm: 0 1px 3px rgba(0,0,0,0.08);
    --shadow-md: 0 4px 16px rgba(0,0,0,0.1);
    --shadow-lg: 0 8px 32px rgba(0,0,0,0.12);

    --transition: 0.2s ease;
    --font: -apple-system, BlinkMacSystemFont, 'Segoe UI', 'PingFang SC', 'Hiragino Sans GB', 'Microsoft YaHei', sans-serif;
    --font-mono: 'SF Mono', 'Fira Code', 'Consolas', monospace;
}

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

html, body {
    height: 100%;
    font-family: var(--font);
    font-size: 15px;
    color: var(--text-primary);
    background: var(--bg);
    -webkit-font-smoothing: antialiased;
    overflow: hidden;
}

#app {
    display: flex;
    height: 100vh;
    width: 100vw;
}

/* ====== Scrollbar ====== */
::-webkit-scrollbar { width: 6px; height: 6px; }
::-webkit-scrollbar-track { background: transparent; }
::-webkit-scrollbar-thumb { background: var(--text-tertiary); border-radius: 3px; }
::-webkit-scrollbar-thumb:hover { background: var(--text-secondary); }

/* ====== Mobile Header ====== */
.mobile-header {
    position: fixed;
    top: 0; left: 0; right: 0;
    height: 50px;
    background: var(--sidebar-bg);
    border-bottom: 1px solid var(--border);
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 0 12px;
    z-index: 200;
}

.app-title-sm {
    font-size: 17px;
    font-weight: 600;
    color: var(--text-primary);
}

/* ====== Sidebar ====== */
.sidebar {
    width: var(--sidebar-width);
    min-width: var(--sidebar-width);
    height: 100vh;
    background: var(--sidebar-bg);
    border-right: 1px solid var(--border);
    display: flex;
    flex-direction: column;
    overflow: hidden;
    flex-shrink: 0;
}

.sidebar-header {
    padding: 20px 18px 12px;
    border-bottom: 1px solid var(--border);
}

.app-title {
    font-size: 20px;
    font-weight: 700;
    color: var(--text-primary);
    display: flex;
    align-items: center;
    gap: 8px;
}

.logo { font-size: 24px; }

/* ====== Search ====== */
.search-box {
    padding: 12px 14px;
    position: relative;
}

.search-icon {
    position: absolute;
    left: 24px;
    top: 50%;
    transform: translateY(-50%);
    color: var(--text-tertiary);
    pointer-events: none;
}

.search-input {
    width: 100%;
    padding: 8px 30px 8px 34px;
    border: 1px solid var(--border);
    border-radius: 20px;
    font-size: 14px;
    outline: none;
    background: var(--bg);
    color: var(--text-primary);
    transition: border-color var(--transition);
}

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

.search-clear {
    position: absolute;
    right: 24px;
    top: 50%;
    transform: translateY(-50%);
    border: none;
    background: none;
    font-size: 18px;
    color: var(--text-tertiary);
    cursor: pointer;
    line-height: 1;
}

/* ====== Search Results ====== */
.search-results {
    flex: 1;
    overflow-y: auto;
    padding: 0 8px 8px;
}

.search-results-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 8px 10px;
    font-size: 13px;
    color: var(--text-secondary);
}

.search-item {
    display: flex;
    align-items: center;
    gap: 8px;
    padding: 10px 12px;
    border-radius: var(--radius-sm);
    cursor: pointer;
    transition: background var(--transition);
}

.search-item:hover { background: var(--bg); }
.search-item.active { background: var(--primary-light); color: var(--primary); }

/* ====== Tree ====== */
.tree-container {
    flex: 1;
    overflow-y: auto;
    display: flex;
    flex-direction: column;
}

.tree-actions {
    display: flex;
    gap: 8px;
    padding: 8px 14px;
}

.tree-list {
    flex: 1;
    overflow-y: auto;
    padding: 0 6px 16px;
}

/* Tree node */
.tree-node { user-select: none; }

.tree-node-row {
    display: flex;
    align-items: center;
    padding: 6px 10px;
    border-radius: var(--radius-sm);
    cursor: pointer;
    transition: background var(--transition);
    gap: 4px;
}

.tree-node-row:hover { background: var(--bg); }
.tree-node-row.active { background: var(--primary-light); }

.tree-toggle {
    width: 20px;
    height: 20px;
    display: flex;
    align-items: center;
    justify-content: center;
    flex-shrink: 0;
    color: var(--text-tertiary);
    transition: transform var(--transition);
}

.tree-toggle.expanded { transform: rotate(90deg); }
.tree-toggle.hidden { visibility: hidden; }

.tree-node-icon {
    font-size: 16px;
    flex-shrink: 0;
}

.tree-node-name {
    flex: 1;
    font-size: 14px;
    overflow: hidden;
    text-overflow: ellipsis;
    white-space: nowrap;
}

.tree-node-menu {
    opacity: 0;
    display: flex;
    gap: 2px;
    transition: opacity var(--transition);
}

.tree-node-row:hover .tree-node-menu { opacity: 1; }

.tree-node-children {
    padding-left: 16px;
}

/* ====== Context Menu Button ====== */
.ctx-btn {
    width: 24px;
    height: 24px;
    border: none;
    background: none;
    border-radius: 4px;
    display: flex;
    align-items: center;
    justify-content: center;
    cursor: pointer;
    color: var(--text-secondary);
    transition: all var(--transition);
    padding: 0;
}

.ctx-btn:hover {
    background: rgba(0,0,0,0.08);
    color: var(--text-primary);
}

.ctx-btn.danger:hover {
    background: rgba(255,59,48,0.1);
    color: var(--danger);
}

/* ====== Dropdown Menu ====== */
.dropdown-menu {
    position: absolute;
    right: 0;
    top: 100%;
    background: var(--sidebar-bg);
    border: 1px solid var(--border);
    border-radius: var(--radius);
    box-shadow: var(--shadow-md);
    min-width: 140px;
    z-index: 100;
    padding: 4px;
    animation: fadeIn 0.15s ease;
}

.dropdown-item {
    display: flex;
    align-items: center;
    gap: 8px;
    padding: 8px 12px;
    font-size: 13px;
    border: none;
    background: none;
    width: 100%;
    text-align: left;
    cursor: pointer;
    border-radius: var(--radius-sm);
    color: var(--text-primary);
    transition: background var(--transition);
}

.dropdown-item:hover { background: var(--bg); }
.dropdown-item.danger { color: var(--danger); }
.dropdown-item.danger:hover { background: rgba(255,59,48,0.06); }

@keyframes fadeIn {
    from { opacity: 0; transform: translateY(-4px); }
    to { opacity: 1; transform: translateY(0); }
}

/* ====== Main Content ====== */
.main-content {
    flex: 1;
    overflow: hidden;
    display: flex;
    flex-direction: column;
    background: var(--bg);
}

/* ====== Empty State ====== */
.empty-state {
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    height: 100%;
    text-align: center;
    padding: 40px;
}

.empty-icon { font-size: 72px; margin-bottom: 20px; }

.empty-state h2 {
    font-size: 24px;
    font-weight: 600;
    margin-bottom: 8px;
    color: var(--text-primary);
}

.empty-state p {
    color: var(--text-secondary);
    margin-bottom: 24px;
}

.empty-actions { display: flex; gap: 12px; }

.empty-hint {
    text-align: center;
    padding: 32px 16px;
    color: var(--text-tertiary);
    font-size: 14px;
}

.hint-sub {
    font-size: 13px;
    margin-top: 4px;
}

/* ====== Editor ====== */
.editor-container {
    display: flex;
    flex-direction: column;
    height: 100%;
    background: var(--content-bg);
    border-radius: var(--radius) 0 0 var(--radius);
    margin: 8px 0 8px 8px;
    box-shadow: var(--shadow-sm);
    overflow: hidden;
}

.editor-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 12px 20px;
    border-bottom: 1px solid var(--border);
    min-height: 48px;
}

.editor-breadcrumb {
    font-size: 13px;
    color: var(--text-secondary);
    display: flex;
    flex-wrap: wrap;
    gap: 2px;
}

.crumb {
    cursor: pointer;
    transition: color var(--transition);
}

.crumb:hover { color: var(--primary); }
.crumb-sep { color: var(--text-tertiary); margin: 0 2px; }

.editor-actions {
    display: flex;
    align-items: center;
    gap: 4px;
}

.save-status {
    font-size: 12px;
    color: var(--success);
    margin-left: 8px;
    animation: fadeIn 0.3s ease;
}

.editor-title-bar {
    padding: 16px 20px 8px;
}

.editor-title {
    width: 100%;
    font-size: 24px;
    font-weight: 700;
    border: none;
    outline: none;
    background: transparent;
    color: var(--text-primary);
    font-family: var(--font);
}

.editor-title::placeholder { color: var(--text-tertiary); }

/* Editor body */
.editor-body {
    flex: 1;
    display: flex;
    overflow: hidden;
}

.editor-body.mode-edit .edit-pane { flex: 1; }
.editor-body.mode-preview .preview-pane { flex: 1; }
.editor-body.mode-split .edit-pane,
.editor-body.mode-split .preview-pane { flex: 1; }
.editor-body.mode-split .edit-pane { border-right: 1px solid var(--border); }

.edit-pane { display: flex; flex-direction: column; min-width: 0; }
.preview-pane { overflow-y: auto; min-width: 0; }

.editor-textarea {
    flex: 1;
    width: 100%;
    padding: 16px 20px;
    border: none;
    outline: none;
    resize: none;
    font-family: var(--font-mono);
    font-size: 14px;
    line-height: 1.7;
    color: var(--text-primary);
    background: transparent;
    tab-size: 4;
}

.editor-textarea::placeholder { color: var(--text-tertiary); }

/* ====== Markdown Preview ====== */
.markdown-body {
    padding: 16px 24px 40px;
    font-size: 15px;
    line-height: 1.75;
    color: var(--text-primary);
    word-wrap: break-word;
}

.markdown-body h1 { font-size: 28px; margin: 24px 0 16px; padding-bottom: 8px; border-bottom: 1px solid var(--border); }
.markdown-body h2 { font-size: 22px; margin: 20px 0 12px; padding-bottom: 6px; border-bottom: 1px solid var(--border); }
.markdown-body h3 { font-size: 18px; margin: 16px 0 8px; }
.markdown-body h4 { font-size: 16px; margin: 14px 0 6px; }
.markdown-body p { margin: 0 0 12px; }
.markdown-body ul, .markdown-body ol { padding-left: 24px; margin: 0 0 12px; }
.markdown-body li { margin: 4px 0; }
.markdown-body blockquote {
    margin: 0 0 12px;
    padding: 8px 16px;
    border-left: 4px solid var(--primary);
    background: var(--primary-light);
    color: var(--text-secondary);
    border-radius: 0 var(--radius-sm) var(--radius-sm) 0;
}
.markdown-body code {
    background: #f0f0f3;
    padding: 2px 6px;
    border-radius: 4px;
    font-family: var(--font-mono);
    font-size: 0.9em;
    color: #d63384;
}
.markdown-body pre {
    background: #f6f8fa;
    border-radius: var(--radius);
    padding: 16px;
    margin: 0 0 16px;
    overflow-x: auto;
}
.markdown-body pre code {
    background: none;
    padding: 0;
    color: inherit;
    font-size: 13px;
    line-height: 1.5;
}
.markdown-body table {
    width: 100%;
    border-collapse: collapse;
    margin: 0 0 16px;
}
.markdown-body th, .markdown-body td {
    border: 1px solid var(--border);
    padding: 8px 12px;
    text-align: left;
}
.markdown-body th { background: var(--bg); font-weight: 600; }
.markdown-body img { max-width: 100%; border-radius: var(--radius); }
.markdown-body a { color: var(--primary); text-decoration: none; }
.markdown-body a:hover { text-decoration: underline; }
.markdown-body hr { border: none; border-top: 1px solid var(--border); margin: 20px 0; }

/* ====== Folder Content ====== */
.folder-content { flex: 1; overflow-y: auto; padding: 20px; }

.folder-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 20px;
    flex-wrap: wrap;
    gap: 12px;
}

.folder-header h2 { font-size: 20px; }
.folder-actions { display: flex; gap: 8px; }

.folder-children { display: grid; gap: 8px; }

.folder-child-item {
    display: flex;
    align-items: center;
    gap: 12px;
    padding: 14px 16px;
    background: var(--bg);
    border-radius: var(--radius);
    cursor: pointer;
    transition: all var(--transition);
}

.folder-child-item:hover {
    background: var(--primary-light);
    transform: translateX(2px);
}

.item-icon { font-size: 16px; flex-shrink: 0; }
.item-icon-lg { font-size: 28px; flex-shrink: 0; }
.item-name { flex: 1; font-size: 14px; overflow: hidden; text-overflow: ellipsis; white-space: nowrap; }
.item-date { font-size: 12px; color: var(--text-tertiary); flex-shrink: 0; }

/* ====== Buttons ====== */
.btn {
    display: inline-flex;
    align-items: center;
    gap: 6px;
    padding: 10px 20px;
    border: none;
    border-radius: var(--radius);
    font-size: 14px;
    font-weight: 500;
    cursor: pointer;
    transition: all var(--transition);
    font-family: var(--font);
}

.btn-sm {
    display: inline-flex;
    align-items: center;
    gap: 4px;
    padding: 6px 12px;
    border: none;
    border-radius: var(--radius-sm);
    font-size: 12px;
    font-weight: 500;
    cursor: pointer;
    transition: all var(--transition);
    font-family: var(--font);
}

.btn-primary, .btn-sm.btn-primary { background: var(--primary); color: #fff; }
.btn-primary:hover, .btn-sm.btn-primary:hover { background: var(--primary-hover); }
.btn-success, .btn-sm.btn-success { background: var(--success); color: #fff; }
.btn-success:hover, .btn-sm.btn-success:hover { background: var(--success-hover); }
.btn-danger, .btn-sm.btn-danger { background: var(--danger); color: #fff; }
.btn-danger:hover, .btn-sm.btn-danger:hover { background: var(--danger-hover); }
.btn-default { background: var(--bg); color: var(--text-primary); border: 1px solid var(--border); }
.btn-default:hover { background: #eee; }

.btn-text {
    background: none;
    border: none;
    color: var(--primary);
    font-size: 13px;
    cursor: pointer;
    padding: 0;
    font-family: var(--font);
}

.btn-text:hover { text-decoration: underline; }

.btn-icon {
    width: 34px;
    height: 34px;
    border: none;
    background: none;
    border-radius: var(--radius-sm);
    display: flex;
    align-items: center;
    justify-content: center;
    cursor: pointer;
    color: var(--text-secondary);
    transition: all var(--transition);
}

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

/* ====== Modal ====== */
.modal-overlay {
    position: fixed;
    inset: 0;
    background: rgba(0,0,0,0.4);
    display: flex;
    align-items: center;
    justify-content: center;
    z-index: 1000;
    animation: fadeIn 0.15s ease;
}

.modal {
    background: var(--content-bg);
    border-radius: 12px;
    padding: 24px;
    width: 90%;
    max-width: 400px;
    box-shadow: var(--shadow-lg);
}

.modal h3 {
    font-size: 18px;
    margin-bottom: 16px;
}

.modal p {
    font-size: 14px;
    color: var(--text-secondary);
    margin-bottom: 20px;
    line-height: 1.6;
}

.modal-input {
    width: 100%;
    padding: 10px 14px;
    border: 1px solid var(--border);
    border-radius: var(--radius);
    font-size: 15px;
    outline: none;
    margin-bottom: 20px;
    font-family: var(--font);
    transition: border-color var(--transition);
}

.modal-input:focus { border-color: var(--primary); }

.modal-actions {
    display: flex;
    justify-content: flex-end;
    gap: 10px;
}

/* ====== Sidebar Overlay (Mobile) ====== */
.sidebar-overlay {
    position: fixed;
    inset: 0;
    background: rgba(0,0,0,0.3);
    z-index: 99;
}

/* ====== Responsive ====== */
@media (max-width: 768px) {
    #app { flex-direction: column; }

    .sidebar {
        position: fixed;
        top: 50px;
        left: 0;
        bottom: 0;
        z-index: 100;
        transform: translateX(-100%);
        transition: transform 0.3s ease;
        box-shadow: var(--shadow-lg);
    }

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

    .sidebar-header { display: none; }

    .main-content {
        margin-top: 50px;
        height: calc(100vh - 50px);
    }

    .editor-container {
        margin: 0;
        border-radius: 0;
    }

    .editor-body.mode-split {
        flex-direction: column;
    }

    .editor-body.mode-split .edit-pane {
        border-right: none;
        border-bottom: 1px solid var(--border);
    }

    .editor-title { font-size: 20px; }

    .folder-header { flex-direction: column; align-items: flex-start; }
}

@media (min-width: 769px) {
    .mobile-header { display: none !important; }
}

/* ====== Login Page ====== */
.login-page {
    display: flex;
    align-items: center;
    justify-content: center;
    width: 100vw;
    height: 100vh;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
}

.login-card {
    background: #fff;
    border-radius: 16px;
    padding: 48px 40px;
    width: 90%;
    max-width: 380px;
    box-shadow: 0 20px 60px rgba(0,0,0,0.2);
    text-align: center;
}

.login-logo { font-size: 56px; margin-bottom: 8px; }

.login-card h2 {
    font-size: 24px;
    font-weight: 700;
    color: var(--text-primary);
    margin-bottom: 4px;
}

.login-subtitle {
    color: var(--text-secondary);
    font-size: 14px;
    margin-bottom: 28px;
}

.login-input {
    width: 100%;
    padding: 12px 16px;
    border: 1px solid var(--border);
    border-radius: var(--radius);
    font-size: 15px;
    outline: none;
    margin-bottom: 14px;
    font-family: var(--font);
    transition: border-color var(--transition);
    background: var(--bg);
}

.login-input:focus { border-color: var(--primary); background: #fff; }

.login-error {
    color: var(--danger);
    font-size: 13px;
    margin-bottom: 12px;
    text-align: left;
}

.login-btn {
    width: 100%;
    padding: 12px;
    font-size: 16px;
    margin-top: 4px;
}

.login-btn:disabled {
    opacity: 0.6;
    cursor: not-allowed;
}

/* ====== User Bar ====== */
.user-bar {
    display: flex;
    align-items: center;
    gap: 8px;
    margin-top: 10px;
    padding: 8px 10px;
    background: var(--bg);
    border-radius: var(--radius);
}

.user-avatar {
    width: 28px;
    height: 28px;
    border-radius: 50%;
    background: var(--primary);
    color: #fff;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 13px;
    font-weight: 600;
    flex-shrink: 0;
}

.user-name {
    flex: 1;
    font-size: 13px;
    color: var(--text-secondary);
    overflow: hidden;
    text-overflow: ellipsis;
    white-space: nowrap;
}

.btn-logout {
    width: 28px;
    height: 28px;
    color: var(--text-tertiary);
}

.btn-logout:hover { color: var(--danger); background: rgba(255,59,48,0.08); }

/* ====== Drag & Drop ====== */
.tree-node-row[draggable="true"] { cursor: grab; }
.tree-node-row[draggable="true"]:active { cursor: grabbing; }

.tree-node-row.dragging {
    opacity: 0.35;
}

.tree-node-row.drop-before {
    box-shadow: inset 0 2px 0 0 var(--primary);
}

.tree-node-row.drop-after {
    box-shadow: inset 0 -2px 0 0 var(--primary);
}

.tree-node-row.drop-inside {
    background: var(--primary-light);
    outline: 2px dashed var(--primary);
    outline-offset: -2px;
    border-radius: var(--radius-sm);
}

.root-drop-zone {
    margin: 8px 10px;
    padding: 12px;
    border: 2px dashed transparent;
    border-radius: var(--radius);
    text-align: center;
    font-size: 12px;
    color: transparent;
    transition: all var(--transition);
}

.root-drop-zone.active {
    border-color: var(--primary);
    background: var(--primary-light);
    color: var(--primary);
}

/* ====== Utility ====== */
.fade-enter-active, .fade-leave-active { transition: opacity 0.2s; }
.fade-enter-from, .fade-leave-to { opacity: 0; }