/* ============================================
   CSS Variables & Reset
   ============================================ */
:root {
    --bg-primary: #f5f7fa;
    --bg-secondary: #ffffff;
    --bg-tertiary: #e8ecf1;
    --text-primary: #1a1a2e;
    --text-secondary: #4a4a68;
    --text-muted: #8888a0;
    --border-color: #e0e4e8;
    --accent-color: #6366f1;
    --accent-hover: #4f46e5;
    --danger-color: #ef4444;
    --danger-hover: #dc2626;
}

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

body {
    font-family: 'Segoe UI', -apple-system, BlinkMacSystemFont, sans-serif;
    background-color: var(--bg-primary);
    color: var(--text-primary);
    line-height: 1.6;
    overflow: hidden;
}

/* ============================================
   App Container Layout
   ============================================ */
.app-container {
    display: flex;
    flex-direction: column;
    height: 100vh;
}

/* ============================================
   Header Styles
   ============================================ */
.header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 12px 24px;
    background-color: var(--bg-secondary);
    border-bottom: 1px solid var(--border-color);
}

.logo {
    display: flex;
    align-items: center;
    gap: 10px;
}

.logo-icon {
    font-size: 28px;
}

.logo h1 {
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--accent-color);
}

/* ============================================
   Button Styles
   ============================================ */
.btn {
    display: inline-flex;
    align-items: center;
    gap: 6px;
    padding: 8px 16px;
    border: none;
    border-radius: 8px;
    font-size: 14px;
    font-weight: 500;
    cursor: pointer;
    transition: all 0.2s ease;
}

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

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

.btn-secondary {
    background-color: var(--bg-tertiary);
    color: var(--text-primary);
    border: 1px solid var(--border-color);
}

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

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

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

/* ============================================
   Main Content - Three Panel Layout
   ============================================ */
.main-content {
    display: flex;
    flex: 1;
    overflow: hidden;
}

.panel {
    display: flex;
    flex-direction: column;
    background-color: var(--bg-secondary);
    border-right: 1px solid var(--border-color);
    overflow: hidden;
}

.panel:last-child {
    border-right: none;
}

.panel-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 16px;
    background-color: var(--bg-tertiary);
    border-bottom: 1px solid var(--border-color);
}

.panel-header h2 {
    font-size: 1rem;
    font-weight: 600;
}

/* ============================================
   File Panel (Left Panel)
   ============================================ */
.file-panel {
    width: 260px;
    min-width: 200px;
}

.search-container {
    padding: 12px;
    border-bottom: 1px solid var(--border-color);
}

.search-input {
    width: 100%;
    padding: 10px 12px;
    border: 1px solid var(--border-color);
    border-radius: 8px;
    background-color: var(--bg-primary);
    color: var(--text-primary);
    font-size: 14px;
    outline: none;
}

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

.file-list {
    list-style: none;
    overflow-y: auto;
    flex: 1;
    padding: 8px;
}

.file-item {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 12px;
    margin-bottom: 4px;
    border-radius: 8px;
    cursor: pointer;
    transition: all 0.2s ease;
}

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

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

.file-info {
    flex: 1;
    min-width: 0;
}

.file-name {
    font-weight: 500;
    font-size: 14px;
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
}

.file-date {
    font-size: 11px;
    color: var(--text-muted);
    margin-top: 2px;
}

.file-item.active .file-date {
    color: rgba(255, 255, 255, 0.8);
}

.delete-btn {
    padding: 4px 8px;
    background: transparent;
    border: none;
    border-radius: 4px;
    cursor: pointer;
    font-size: 12px;
    opacity: 0;
    transition: opacity 0.2s;
}

.file-item:hover .delete-btn,
.file-item.active .delete-btn {
    opacity: 1;
}

.delete-btn:hover {
    background: rgba(0, 0, 0, 0.1);
}

.empty-files {
    padding: 20px;
    text-align: center;
    color: var(--text-muted);
}

/* ============================================
   Editor Panel (Middle Panel)
   ============================================ */
.editor-panel {
    flex: 1;
    min-width: 300px;
}

.editor-container {
    display: flex;
    flex-direction: column;
    flex: 1;
    padding: 16px;
    overflow: hidden;
}

.file-title-input {
    padding: 12px;
    margin-bottom: 12px;
    border: 2px solid var(--border-color);
    border-radius: 8px;
    background-color: var(--bg-primary);
    color: var(--text-primary);
    font-size: 18px;
    font-weight: 600;
    outline: none;
}

.file-title-input:focus {
    border-color: var(--accent-color);
}

.markdown-editor {
    flex: 1;
    padding: 16px;
    border: 2px solid var(--border-color);
    border-radius: 8px;
    background-color: var(--bg-primary);
    color: var(--text-primary);
    font-family: 'Consolas', 'Monaco', 'Courier New', monospace;
    font-size: 14px;
    line-height: 1.7;
    resize: none;
    outline: none;
}

.markdown-editor:focus {
    border-color: var(--accent-color);
}

/* ============================================
   Preview Panel (Right Panel)
   ============================================ */
.preview-panel {
    flex: 1;
    min-width: 300px;
}

.preview-content {
    flex: 1;
    padding: 24px;
    overflow-y: auto;
    background-color: var(--bg-primary);
}

.empty-state {
    display: flex;
    align-items: center;
    justify-content: center;
    height: 100%;
    color: var(--text-muted);
    font-style: italic;
}

/* ============================================
   Markdown Preview Styles
   ============================================ */
.preview-content h1,
.preview-content h2,
.preview-content h3,
.preview-content h4,
.preview-content h5,
.preview-content h6 {
    margin-top: 24px;
    margin-bottom: 16px;
    font-weight: 600;
    color: var(--text-primary);
}

.preview-content h1 {
    font-size: 2em;
    border-bottom: 1px solid var(--border-color);
    padding-bottom: 0.3em;
}

.preview-content h2 {
    font-size: 1.5em;
    border-bottom: 1px solid var(--border-color);
    padding-bottom: 0.3em;
}

.preview-content h3 {
    font-size: 1.25em;
}

.preview-content h4 {
    font-size: 1em;
}

.preview-content h5 {
    font-size: 0.875em;
}

.preview-content h6 {
    font-size: 0.85em;
    color: var(--text-muted);
}

.preview-content p {
    margin-bottom: 16px;
    color: var(--text-secondary);
}

.preview-content a {
    color: var(--accent-color);
    text-decoration: none;
}

.preview-content a:hover {
    text-decoration: underline;
}

.preview-content ul,
.preview-content ol {
    margin-bottom: 16px;
    padding-left: 2em;
    color: var(--text-secondary);
}

.preview-content li {
    margin-bottom: 4px;
}

.preview-content blockquote {
    margin: 16px 0;
    padding: 12px 20px;
    border-left: 4px solid var(--accent-color);
    background-color: var(--bg-tertiary);
    color: var(--text-secondary);
}

.preview-content blockquote p {
    margin-bottom: 0;
}

/* Inline code */
.preview-content code:not(pre code) {
    padding: 2px 6px;
    background-color: rgba(110, 118, 129, 0.2);
    border-radius: 4px;
    font-family: 'Consolas', 'Monaco', 'Courier New', monospace;
    font-size: 0.9em;
    color: #e85d5d;
}

/* Code blocks */
.preview-content pre {
    margin: 16px 0;
    border-radius: 8px;
    overflow: hidden;
}

.preview-content pre code {
    display: block;
    padding: 16px !important;
    font-family: 'Consolas', 'Monaco', 'Courier New', monospace;
    font-size: 14px;
    line-height: 1.6;
    overflow-x: auto;
}

/* Tables */
.preview-content table {
    width: 100%;
    border-collapse: collapse;
    margin: 16px 0;
}

.preview-content th,
.preview-content td {
    border: 1px solid var(--border-color);
    padding: 10px 12px;
    text-align: left;
}

.preview-content th {
    background-color: var(--bg-tertiary);
    font-weight: 600;
}

.preview-content tr:nth-child(even) {
    background-color: var(--bg-tertiary);
}

/* Task lists */
.preview-content input[type="checkbox"] {
    margin-right: 8px;
    cursor: pointer;
}

/* Images */
.preview-content img {
    max-width: 100%;
    height: auto;
    border-radius: 8px;
    margin: 16px 0;
}

/* Horizontal rule */
.preview-content hr {
    border: none;
    border-top: 2px solid var(--border-color);
    margin: 24px 0;
}

/* Strong and emphasis */
.preview-content strong {
    font-weight: 600;
    color: var(--text-primary);
}

.preview-content em {
    font-style: italic;
}

/* Strikethrough */
.preview-content del {
    text-decoration: line-through;
    color: var(--text-muted);
}

/* ============================================
   Footer
   ============================================ */
.footer {
    padding: 10px 24px;
    background-color: var(--bg-secondary);
    border-top: 1px solid var(--border-color);
    text-align: center;
    font-size: 12px;
    color: var(--text-muted);
}

/* ============================================
   Modal
   ============================================ */
.modal {
    display: none;
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background-color: rgba(0, 0, 0, 0.5);
    justify-content: center;
    align-items: center;
    z-index: 1000;
}

.modal.show {
    display: flex;
}

.modal-content {
    background-color: var(--bg-secondary);
    padding: 24px;
    border-radius: 12px;
    max-width: 400px;
    width: 90%;
    box-shadow: 0 20px 25px -5px rgba(0, 0, 0, 0.1);
}

.modal-content h3 {
    margin-bottom: 12px;
}

.modal-content p {
    margin-bottom: 20px;
    color: var(--text-secondary);
}

.modal-actions {
    display: flex;
    justify-content: flex-end;
    gap: 12px;
}

/* ============================================
   Responsive Design
   ============================================ */
@media (max-width: 768px) {
    .main-content {
        flex-direction: column;
    }

    .file-panel {
        width: 100%;
        max-height: 30vh;
    }

    .editor-panel,
    .preview-panel {
        min-width: 100%;
    }
}