/* CSS Variables */
:root {
    --primary-color: #3b82f6;
    --primary-hover: #2563eb;
    --secondary-color: #64748b;
    --secondary-hover: #475569;
    --background-color: #0f172a;
    --surface-color: #1e293b;
    --surface-hover: #334155;
    --border-color: #334155;
    --text-primary: #f1f5f9;
    --text-secondary: #94a3b8;
    --text-muted: #64748b;
    --editor-bg: #1e293b;
    --preview-bg: #0f172a;
    --success-color: #22c55e;
    --warning-color: #f59e0b;
    --error-color: #ef4444;
    --header-height: 56px;
    --toolbar-height: 44px;
    --footer-height: 40px;
    --panel-header-height: 36px;
    --font-mono: 'Fira Code', 'Cascadia Code', 'JetBrains Mono', 'Consolas', monospace;
    --font-sans: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
    --transition-fast: 150ms ease;
    --transition-normal: 250ms ease;
    --shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.3);
    --shadow-md: 0 4px 6px rgba(0, 0, 0, 0.4);
    --shadow-lg: 0 10px 15px rgba(0, 0, 0, 0.5);
}

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

/* Base Styles */
html, body {
    height: 100%;
    overflow: hidden;
}

body {
    font-family: var(--font-sans);
    background-color: var(--background-color);
    color: var(--text-primary);
    line-height: 1.6;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

/* App Container */
.app-container {
    display: flex;
    flex-direction: column;
    height: 100vh;
    max-height: 100vh;
    overflow: hidden;
}

/* Header */
.header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    height: var(--header-height);
    padding: 0 16px;
    background-color: var(--surface-color);
    border-bottom: 1px solid var(--border-color);
    flex-shrink: 0;
}

.header-left {
    display: flex;
    align-items: center;
    gap: 12px;
}

.logo {
    width: 32px;
    height: 32px;
    border-radius: 6px;
}

.header h1 {
    font-size: 1.25rem;
    font-weight: 600;
    color: var(--text-primary);
}

.header-right {
    display: flex;
    align-items: center;
    gap: 8px;
}

/* Buttons */
.btn {
    display: inline-flex;
    align-items: center;
    gap: 8px;
    padding: 8px 16px;
    border: none;
    border-radius: 6px;
    font-size: 0.875rem;
    font-weight: 500;
    cursor: pointer;
    transition: all var(--transition-fast);
    white-space: nowrap;
}

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

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

.btn-secondary {
    background-color: var(--surface-hover);
    color: var(--text-primary);
}

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

.mobile-only {
    display: none;
}

/* Toolbar */
.toolbar {
    display: flex;
    align-items: center;
    gap: 4px;
    height: var(--toolbar-height);
    padding: 0 12px;
    background-color: var(--surface-color);
    border-bottom: 1px solid var(--border-color);
    flex-shrink: 0;
    overflow-x: auto;
    scrollbar-width: none;
}

.toolbar::-webkit-scrollbar {
    display: none;
}

.toolbar-group {
    display: flex;
    align-items: center;
    gap: 2px;
}

.toolbar-separator {
    width: 1px;
    height: 24px;
    background-color: var(--border-color);
    margin: 0 6px;
}

.toolbar-btn {
    display: flex;
    align-items: center;
    justify-content: center;
    width: 32px;
    height: 32px;
    border: none;
    border-radius: 4px;
    background-color: transparent;
    color: var(--text-secondary);
    cursor: pointer;
    transition: all var(--transition-fast);
    font-size: 0.875rem;
}

.toolbar-btn:hover {
    background-color: var(--surface-hover);
    color: var(--text-primary);
}

.toolbar-btn:active {
    transform: scale(0.95);
}

.toolbar-btn svg {
    width: 16px;
    height: 16px;
}

/* Main Content */
.main-content {
    display: flex;
    flex: 1;
    min-height: 0;
    overflow: hidden;
}

/* Panels */
.panel {
    display: flex;
    flex-direction: column;
    flex: 1;
    min-width: 0;
    overflow: hidden;
}

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

.panel-title {
    font-size: 0.75rem;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.05em;
    color: var(--text-secondary);
}

.char-count {
    font-size: 0.75rem;
    color: var(--text-muted);
}

/* Editor */
.editor-panel {
    background-color: var(--editor-bg);
}

.editor {
    flex: 1;
    width: 100%;
    padding: 16px;
    border: none;
    background-color: var(--editor-bg);
    color: var(--text-primary);
    font-family: var(--font-mono);
    font-size: 0.9375rem;
    line-height: 1.7;
    resize: none;
    outline: none;
    tab-size: 4;
}

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

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

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

/* Preview */
.preview-panel {
    background-color: var(--preview-bg);
    border-left: 1px solid var(--border-color);
}

.preview {
    flex: 1;
    padding: 16px 24px;
    overflow-y: auto;
    overflow-x: hidden;
}

/* Markdown Body Styles */
.markdown-body {
    color: var(--text-primary);
    font-size: 1rem;
    line-height: 1.7;
    word-wrap: break-word;
}

.markdown-body h1,
.markdown-body h2,
.markdown-body h3,
.markdown-body h4,
.markdown-body h5,
.markdown-body h6 {
    margin-top: 1.5em;
    margin-bottom: 0.5em;
    font-weight: 600;
    line-height: 1.3;
    color: var(--text-primary);
}

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

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

.markdown-body h3 { font-size: 1.25em; }
.markdown-body h4 { font-size: 1em; }
.markdown-body h5 { font-size: 0.875em; }
.markdown-body h6 { font-size: 0.85em; color: var(--text-secondary); }

.markdown-body p {
    margin-top: 0;
    margin-bottom: 1em;
}

.markdown-body a {
    color: var(--primary-color);
    text-decoration: none;
}

.markdown-body a:hover {
    text-decoration: underline;
}

.markdown-body strong {
    font-weight: 600;
}

.markdown-body em {
    font-style: italic;
}

.markdown-body code {
    padding: 0.2em 0.4em;
    margin: 0;
    font-size: 85%;
    background-color: var(--surface-hover);
    border-radius: 4px;
    font-family: var(--font-mono);
}

.markdown-body pre {
    padding: 16px;
    overflow: auto;
    font-size: 85%;
    line-height: 1.5;
    background-color: var(--surface-color);
    border-radius: 8px;
    margin-bottom: 1em;
}

.markdown-body pre code {
    padding: 0;
    margin: 0;
    font-size: 100%;
    word-break: normal;
    white-space: pre;
    background: transparent;
    border: 0;
}

.markdown-body blockquote {
    margin: 0 0 1em 0;
    padding: 0.5em 1em;
    color: var(--text-secondary);
    border-left: 4px solid var(--primary-color);
    background-color: var(--surface-color);
    border-radius: 0 4px 4px 0;
}

.markdown-body blockquote > :first-child {
    margin-top: 0;
}

.markdown-body blockquote > :last-child {
    margin-bottom: 0;
}

.markdown-body ul,
.markdown-body ol {
    margin-top: 0;
    margin-bottom: 1em;
    padding-left: 2em;
}

.markdown-body li {
    margin-bottom: 0.25em;
}

.markdown-body li + li {
    margin-top: 0.25em;
}

.markdown-body ul ul,
.markdown-body ul ol,
.markdown-body ol ol,
.markdown-body ol ul {
    margin-top: 0;
    margin-bottom: 0;
}

.markdown-body hr {
    height: 2px;
    padding: 0;
    margin: 1.5em 0;
    background-color: var(--border-color);
    border: 0;
}

.markdown-body table {
    width: 100%;
    margin-bottom: 1em;
    border-collapse: collapse;
    border-spacing: 0;
    overflow: auto;
}

.markdown-body table th,
.markdown-body table td {
    padding: 8px 12px;
    border: 1px solid var(--border-color);
}

.markdown-body table th {
    font-weight: 600;
    background-color: var(--surface-color);
}

.markdown-body table tr {
    background-color: var(--preview-bg);
}

.markdown-body table tr:nth-child(2n) {
    background-color: var(--surface-color);
}

.markdown-body img {
    max-width: 100%;
    height: auto;
    border-radius: 8px;
}

.markdown-body input[type="checkbox"] {
    margin-right: 0.5em;
    vertical-align: middle;
}

/* Task list items */
.markdown-body ul.contains-task-list {
    list-style-type: none;
    padding-left: 0;
}

.markdown-body li.task-list-item {
    display: flex;
    align-items: flex-start;
    gap: 8px;
}

/* Footer */
.footer {
    display: flex;
    align-items: center;
    justify-content: center;
    height: var(--footer-height);
    padding: 0 16px;
    background-color: var(--surface-color);
    border-top: 1px solid var(--border-color);
    flex-shrink: 0;
}

.footer p {
    font-size: 0.8125rem;
    color: var(--text-secondary);
}

.footer a {
    color: var(--primary-color);
    text-decoration: none;
    font-weight: 500;
    transition: color var(--transition-fast);
}

.footer a:hover {
    color: var(--primary-hover);
    text-decoration: underline;
}

/* Scrollbar Styles */
.preview::-webkit-scrollbar,
.editor::-webkit-scrollbar {
    width: 8px;
}

.preview::-webkit-scrollbar-track,
.editor::-webkit-scrollbar-track {
    background: var(--surface-color);
}

.preview::-webkit-scrollbar-thumb,
.editor::-webkit-scrollbar-thumb {
    background: var(--surface-hover);
    border-radius: 4px;
}

.preview::-webkit-scrollbar-thumb:hover,
.editor::-webkit-scrollbar-thumb:hover {
    background: var(--secondary-color);
}

/* Mobile Responsive */
@media (max-width: 768px) {
    .header h1 {
        font-size: 1rem;
    }

    .btn span {
        display: none;
    }

    .btn {
        padding: 8px;
    }

    .mobile-only {
        display: flex;
    }

    .toolbar {
        padding: 0 8px;
    }

    .toolbar-separator {
        margin: 0 4px;
    }

    .main-content {
        flex-direction: column;
    }

    .resizer {
        display: none;
    }

    .panel {
        position: absolute;
        top: calc(var(--header-height) + var(--toolbar-height));
        left: 0;
        right: 0;
        bottom: var(--footer-height);
        transition: opacity var(--transition-normal), visibility var(--transition-normal);
    }

    .editor-panel {
        z-index: 2;
    }

    .preview-panel {
        z-index: 1;
        border-left: none;
    }

    .panel.hidden {
        opacity: 0;
        visibility: hidden;
        pointer-events: none;
    }

    .preview {
        padding: 16px;
    }
}

/* Small mobile */
@media (max-width: 480px) {
    .toolbar-group:nth-child(n+7) {
        display: none;
    }

    .header-left {
        gap: 8px;
    }

    .logo {
        width: 28px;
        height: 28px;
    }
}

/* Focus States */
.btn:focus-visible,
.toolbar-btn:focus-visible {
    outline: 2px solid var(--primary-color);
    outline-offset: 2px;
}

.editor:focus {
    outline: none;
}

/* Print Styles */
@media print {
    .header,
    .toolbar,
    .editor-panel,
    .resizer,
    .footer {
        display: none;
    }

    .preview-panel {
        border: none;
        position: static;
    }

    .panel-header {
        display: none;
    }

    .preview {
        padding: 0;
    }

    .markdown-body {
        color: black;
    }

    .markdown-body pre,
    .markdown-body code {
        background-color: #f4f4f4;
    }
}

/* Placeholder message for empty preview */
.preview:empty::before {
    content: 'Preview will appear here...';
    color: var(--text-muted);
    font-style: italic;
}

/* Highlight.js overrides for better dark theme integration */
.hljs {
    background: transparent !important;
    padding: 0 !important;
}