:root {
    --header-height: 64px;
    --sidebar-width: 320px;
    --border-color: #e1e4e8;
    --bg-light: #f6f8fa;
    --accent-color: #0366d6;
    --accent-hover: #0255b3;
    --text-main: #24292e;
    --text-muted: #586069;
    --radius: 8px;
    --shadow: 0 2px 10px rgba(0,0,0,0.05);
}

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

body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
    background-color: #fff;
    color: var(--text-main);
    height: 100vh;
    display: flex;
    flex-direction: column;
    overflow: hidden;
}

/* Header */
.app-header {
    height: var(--header-height);
    background-color: #fff;
    padding: 0 1.5rem;
    display: flex;
    justify-content: space-between;
    align-items: center;
    border-bottom: 1px solid var(--border-color);
    box-shadow: 0 1px 2px rgba(0,0,0,0.03);
    z-index: 1000;
}

.header-left, .header-right {
    flex: 1;
    display: flex;
    align-items: center;
}

.header-center {
    flex: 2;
    display: flex;
    justify-content: center;
    align-items: center;
}

.header-right {
    justify-content: flex-end;
    gap: 1.5rem;
}

.logo {
    font-size: 1.15rem;
    font-weight: 800;
    display: flex;
    align-items: center;
    gap: 0.6rem;
    color: var(--text-main);
    white-space: nowrap;
}

.github-link {
    display: flex;
    align-items: center;
    gap: 0.4rem;
    color: var(--text-muted);
    text-decoration: none;
    font-size: 0.85rem;
    font-weight: 600;
    transition: color 0.2s;
    white-space: nowrap;
}

.github-link:hover {
    color: var(--accent-color);
}

.actions {
    display: flex;
    gap: 0.75rem;
}

.btn-primary, .btn-secondary {
    border: 1px solid rgba(27,31,35,0.1);
    padding: 0.5rem 1rem;
    border-radius: var(--radius);
    font-weight: 600;
    cursor: pointer;
    font-size: 0.8rem;
    transition: all 0.2s cubic-bezier(0.3, 0, 0.5, 1);
    white-space: nowrap;
}

.btn-primary { 
    background-color: var(--accent-color); 
    color: #fff;
}
.btn-primary:hover { 
    background-color: var(--accent-hover); 
    transform: translateY(-1px);
}

.btn-secondary { 
    background-color: #fff; 
    color: var(--text-main);
}
.btn-secondary:hover { 
    background-color: var(--bg-light);
}

/* Layout Container */
.app-container {
    flex: 1;
    display: flex;
    flex-direction: row;
    overflow: hidden;
}

/* Panels */
.editor-panel, .preview-panel {
    flex: 1;
    display: flex;
    flex-direction: column;
    border-right: 1px solid var(--border-color);
    min-width: 0;
}

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

.panel-header {
    font-size: 0.75rem;
    font-weight: 700;
    letter-spacing: 0.05em;
    text-transform: uppercase;
    color: var(--text-muted);
    padding: 0.75rem 1rem;
    background-color: #fff;
    border-bottom: 1px solid var(--border-color);
    display: flex;
    justify-content: space-between;
    align-items: center;
    gap: 0.5rem;
    min-height: 48px;
}

.spinner {
    width: 16px;
    height: 16px;
    border: 2px solid rgba(0, 0, 0, 0.05);
    border-top-color: var(--accent-color);
    border-radius: 50%;
    animation: spin 0.8s linear infinite, pulse 1.5s ease-in-out infinite;
}

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

@keyframes pulse {
    0% { transform: scale(1); opacity: 1; }
    50% { transform: scale(1.1); opacity: 0.7; }
    100% { transform: scale(1); opacity: 1; }
}

/* CodeMirror Styling */
.CodeMirror {
    flex: 1;
    height: auto;
    font-family: "SFMono-Regular", Consolas, "Liberation Mono", Menlo, monospace;
    font-size: 14px;
    background: #fff !important;
}

/* Preview Panel & Container */
.preview-panel {
    background-color: #525659;
}

#preview-container {
    flex: 1;
    background-color: transparent;
    display: flex;
    justify-content: center;
    align-items: center;
    position: relative;
    padding: 0;
    overflow: hidden;
}

.preview-placeholder {
    color: rgba(255,255,255,0.7);
    text-align: center;
    font-size: 0.95rem;
    background: rgba(255,255,255,0.05);
    padding: 3rem;
    border-radius: var(--radius);
    border: 2px dashed rgba(255,255,255,0.15);
    max-width: 300px;
}

#pdf-preview {
    width: 100%;
    height: 100%;
    border: none;
    background-color: transparent;
    opacity: 0;
    transition: opacity 0.4s ease-out;
}

#pdf-preview[style*="display: block"] {
    opacity: 1;
}

/* Toolbar */
.editor-toolbar {
    display: flex;
    gap: 0.25rem;
    flex-wrap: wrap;
}

.editor-toolbar button {
    background: #fff;
    border: 1px solid var(--border-color);
    padding: 0.25rem 0.5rem;
    border-radius: 4px;
    font-size: 0.7rem;
    font-weight: 600;
    color: var(--text-muted);
    cursor: pointer;
    transition: all 0.2s;
    white-space: nowrap;
}

.editor-toolbar button:hover {
    background-color: var(--bg-light);
    color: var(--text-main);
    border-color: var(--accent-color);
}

.btn-text-danger:hover {
    color: #d73a49 !important;
    border-color: #d73a49 !important;
    background-color: #fff5f5 !important;
}

/* Settings Controls */
.settings-content {
    flex: 1;
    overflow-y: auto;
    padding: 1.25rem;
}

.section-title {
    margin-top: 1.5rem;
    font-size: 0.8rem;
    font-weight: 700;
    color: var(--text-main);
    display: flex;
    align-items: center;
    gap: 0.5rem;
    margin-bottom: 0.75rem;
}

.section-title::after {
    content: "";
    flex: 1;
    height: 1px;
    background-color: var(--border-color);
}

.section-title:first-child {
    margin-top: 0;
}

.control-group {
    margin-bottom: 1rem;
}

.control-group label {
    display: block;
    font-size: 0.75rem;
    font-weight: 600;
    color: var(--text-muted);
    margin-bottom: 0.4rem;
}

.control-group input[type="text"],
.control-group input[type="color"],
.control-group select {
    width: 100%;
    padding: 0.5rem;
    border: 1px solid var(--border-color);
    border-radius: var(--radius);
    font-size: 0.8rem;
    background-color: #fff;
}

.control-group input:focus, .control-group select:focus {
    outline: none;
    border-color: var(--accent-color);
}

.control-group input[type="color"] {
    height: 36px;
    padding: 2px;
}

.control-group.checkbox {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    cursor: pointer;
    font-size: 0.8rem;
    font-weight: 500;
}

.sub-controls {
    padding-left: 1.25rem;
    margin-top: 0.5rem;
    border-left: 2px solid var(--border-color);
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
}

.doc-list-container {
    display: flex;
    gap: 0.4rem;
    align-items: center;
}

#doc-selector {
    flex: 1;
    min-width: 0;
}

.doc-actions {
    display: flex;
    gap: 0.25rem;
}

.doc-actions button {
    width: 32px;
    height: 32px;
    padding: 0;
    display: flex;
    justify-content: center;
    align-items: center;
    font-size: 0.85rem;
}

#new-doc-btn { font-size: 1.1rem; }

.tips-box {
    background-color: #fff;
    border: 1px solid var(--border-color);
    border-radius: var(--radius);
    padding: 0.75rem;
    font-size: 0.75rem;
    line-height: 1.4;
    color: var(--text-muted);
    box-shadow: var(--shadow);
}

.tips-box p { margin-bottom: 0.4rem; }
.tips-box p:last-child { margin-bottom: 0; }
.tips-box code {
    background-color: var(--bg-light);
    padding: 1px 4px;
    border-radius: 3px;
    font-family: monospace;
}

.status-pill {
    padding: 0.25rem 0.75rem;
    border-radius: 20px;
    background-color: #eaf5ff;
    color: var(--accent-color);
    font-size: 0.7rem;
    font-weight: 700;
    border: 1px solid rgba(3, 102, 214, 0.1);
    transition: all 0.3s ease;
}

.status-pill.saved {
    background-color: #f0fff4;
    color: #28a745;
    border-color: rgba(40, 167, 69, 0.1);
}

.status-pill.saved::before {
    content: "● ";
    font-size: 0.6rem;
    vertical-align: middle;
}

/* Responsive Design (RWD) */
@media (max-width: 1200px) {
    .app-container { flex-direction: column; overflow-y: auto; }
    .editor-panel, .preview-panel, .controls-panel { width: 100%; height: auto; flex: none; border: none; border-bottom: 1px solid var(--border-color); }
    .CodeMirror { height: 400px; }
    #preview-container { height: 600px; }
}