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

:root {
    --bg-primary: #1e1e1e;
    --bg-secondary: #252526;
    --bg-tertiary: #2d2d30;
    --text-primary: #cccccc;
    --text-secondary: #858585;
    --border-color: #3e3e42;
    --accent: #007acc;
    --accent-hover: #005999;
    --danger: #d32f2f;
    --danger-hover: #b71c1c;
    --success: #4caf50;
    --shadow: 0 2px 8px rgba(0, 0, 0, 0.3);
    --transition-fast: 0.15s ease;
    --transition-smooth: 0.25s cubic-bezier(0.4, 0, 0.2, 1);
    --toolbar-height: 48px;
    --header-height: 35px;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, sans-serif;
    background: var(--bg-primary);
    color: var(--text-primary);
    height: 100vh;
    overflow: hidden;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
    user-select: none;
}

.app-container {
    display: flex;
    height: 100vh;
    overflow: hidden;
}

/* Боковая панель */
.sidebar {
    width: 280px;
    min-width: 280px;
    background: var(--bg-secondary);
    border-right: 1px solid var(--border-color);
    display: flex;
    flex-direction: column;
    transition: transform var(--transition-smooth), min-width var(--transition-smooth), width var(--transition-smooth);
    will-change: transform;
    overflow: hidden;
}

.sidebar.hidden {
    transform: translateX(-100%);
    min-width: 0;
    width: 0;
    border-right: none;
}

.sidebar-header {
    height: var(--toolbar-height);
    min-height: var(--toolbar-height);
    padding: 0 16px;
    border-bottom: 1px solid var(--border-color);
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.sidebar-header h2 {
    font-size: 13px;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.5px;
    color: var(--text-secondary);
    white-space: nowrap;
}

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

.sidebar-body {
    flex: 1;
    display: flex;
    flex-direction: column;
    overflow: hidden;
}

.btn-open-folder {
    display: flex;
    align-items: center;
    gap: 8px;
    padding: 10px 16px;
    margin: 8px;
    background: var(--bg-tertiary);
    border: 1px dashed var(--border-color);
    border-radius: 6px;
    color: var(--text-primary);
    cursor: pointer;
    font-size: 13px;
    transition: all var(--transition-fast);
    white-space: nowrap;
}

.btn-open-folder:hover {
    background: #3e3e42;
    border-color: var(--accent);
}

.file-list {
    flex: 1;
    overflow-y: auto;
    padding: 4px 8px;
}

.file-item {
    padding: 8px 12px;
    margin: 2px 0;
    cursor: pointer;
    border-radius: 4px;
    font-size: 13px;
    transition: background var(--transition-fast);
    display: flex;
    align-items: center;
    gap: 8px;
    user-select: none;
}

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

.file-item.active {
    background: var(--accent);
    color: white;
}

.file-item .file-icon {
    opacity: 0.7;
    flex-shrink: 0;
    display: flex;
    align-items: center;
}

.file-item .file-name {
    flex: 1;
    overflow: hidden;
    text-overflow: ellipsis;
    white-space: nowrap;
}

.empty-state {
    color: var(--text-secondary);
    font-size: 13px;
    text-align: center;
    padding: 24px 16px;
}

/* Основная область */
.main-area {
    flex: 1;
    display: flex;
    flex-direction: column;
    overflow: hidden;
    min-width: 0;
}

/* Единая панель инструментов */
.toolbar {
    height: var(--toolbar-height);
    min-height: var(--toolbar-height);
    background: var(--bg-secondary);
    border-bottom: 1px solid var(--border-color);
    display: flex;
    align-items: center;
    padding: 0 8px;
    gap: 8px;
}

.toolbar-section {
    display: flex;
    align-items: center;
    gap: 8px;
}

.toolbar-left {
    flex: 1;
    min-width: 0;
}

.toolbar-right {
    flex: 1;
    justify-content: flex-end;
}

.current-file {
    font-size: 13px;
    font-weight: 500;
    color: var(--text-primary);
    overflow: hidden;
    text-overflow: ellipsis;
    white-space: nowrap;
}

.modified-indicator {
    color: var(--accent);
    font-size: 18px;
    line-height: 1;
}

/* Кнопки */
.btn {
    padding: 6px 12px;
    border: 1px solid var(--border-color);
    border-radius: 4px;
    background: var(--bg-tertiary);
    color: var(--text-primary);
    cursor: pointer;
    font-size: 12px;
    font-weight: 500;
    display: flex;
    align-items: center;
    gap: 6px;
    transition: all var(--transition-fast);
    white-space: nowrap;
}

.btn:hover:not(:disabled) {
    background: #3e3e42;
}

.btn:active:not(:disabled) {
    transform: scale(0.98);
}

.btn:disabled {
    opacity: 0.5;
    cursor: not-allowed;
}

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

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

.btn-icon {
    padding: 6px;
    background: transparent;
    border: none;
    color: var(--text-primary);
    cursor: pointer;
    border-radius: 4px;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: background var(--transition-fast);
    flex-shrink: 0;
}

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

/* Редактор и предпросмотр */
.editor-preview-container {
    flex: 1;
    display: flex;
    overflow: hidden;
    position: relative;
}

.editor-pane,
.preview-pane {
    display: flex;
    flex-direction: column;
    min-width: 0;
    overflow: hidden;
}

.editor-pane {
    flex: 1;
}

.preview-pane {
    flex: 1;
}

/* Разделитель */
.resizer {
    width: 4px;
    background: var(--border-color);
    cursor: col-resize;
    transition: background var(--transition-fast);
    position: relative;
    flex-shrink: 0;
}

.resizer:hover,
.resizer.active {
    background: var(--accent);
}

.resizer::after {
    content: '';
    position: absolute;
    top: 0;
    left: -4px;
    right: -4px;
    bottom: 0;
}

/* Скрытые панели */
.editor-pane.hidden {
    display: none;
}

.preview-pane.hidden {
    display: none;
}

/* Заголовки панелей */
.pane-header {
    height: var(--header-height);
    min-height: var(--header-height);
    padding: 0 12px;
    background: var(--bg-tertiary);
    border-bottom: 1px solid var(--border-color);
    font-size: 11px;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.5px;
    color: var(--text-secondary);
    flex-shrink: 0;
    display: flex;
    align-items: center;
    justify-content: space-between;
}

.pane-header span {
    white-space: nowrap;
}

.panel-toggle-btn {
    opacity: 0.7;
    padding: 4px;
}

.panel-toggle-btn:hover {
    opacity: 1;
    background: var(--bg-secondary);
}

.editor-textarea {
    flex: 1;
    background: var(--bg-primary);
    border: none;
    color: var(--text-primary);
    padding: 16px;
    font-family: 'JetBrains Mono', 'Fira Code', 'Consolas', monospace;
    font-size: 14px;
    line-height: 1.6;
    resize: none;
    outline: none;
    tab-size: 4;
    user-select: text;
}

.editor-textarea::placeholder {
    color: var(--text-secondary);
    opacity: 0.5;
}

.preview-content {
    flex: 1;
    padding: 16px;
    overflow-y: auto;
    line-height: 1.7;
    user-select: text;
}

/* Контекстное меню */
.context-menu {
    position: fixed;
    background: var(--bg-secondary);
    border: 1px solid var(--border-color);
    border-radius: 6px;
    box-shadow: var(--shadow);
    min-width: 180px;
    z-index: 1000;
    padding: 4px;
    animation: contextMenuIn 0.15s ease;
}

@keyframes contextMenuIn {
    from {
        opacity: 0;
        transform: scale(0.95);
    }
    to {
        opacity: 1;
        transform: scale(1);
    }
}

.context-menu-item {
    padding: 8px 12px;
    display: flex;
    align-items: center;
    gap: 8px;
    cursor: pointer;
    border-radius: 4px;
    font-size: 13px;
    transition: background var(--transition-fast);
}

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

.context-menu-item.danger {
    color: var(--danger);
}

.context-menu-item.danger:hover {
    background: var(--danger-hover);
}

/* Адаптивность */
@media (max-width: 768px) {
    .sidebar {
        position: fixed;
        left: 0;
        top: var(--toolbar-height);
        height: calc(100vh - var(--toolbar-height));
        z-index: 100;
        box-shadow: var(--shadow);
    }

    .sidebar.hidden {
        transform: translateX(-100%);
    }

    .toolbar-right .btn span,
    .toolbar-right .btn svg + span {
        display: none;
    }

    .toolbar-right .btn {
        padding: 6px;
    }
}

/* Кастомизация скроллбара */
::-webkit-scrollbar {
    width: 8px;
    height: 8px;
}

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

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

::-webkit-scrollbar-thumb:hover {
    background: #555;
}