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

:root {
    --header-height: 56px;
    --pane-header-height: 40px;
    --bg-primary: #1e1e1e;
    --bg-secondary: #252526;
    --bg-tertiary: #2d2d2d;
    --text-primary: #d4d4d4;
    --text-secondary: #858585;
    --accent: #0078d4;
    --accent-hover: #1a8cdf;
    --border-color: #3c3c3c;
    --error-bg: #5a1d1d;
    --error-text: #f48771;
    --success-text: #89d185;
}

html, body {
    height: 100%;
    overflow: hidden;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, sans-serif;
    background: var(--bg-primary);
    color: var(--text-primary);
}

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

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

.logo {
    height: 44px;
    width: auto;
}

.header-text {
    display: flex;
    flex-direction: column;
    gap: 0;
}

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

.subtitle {
    font-size: 0.875rem;
    color: var(--text-secondary);
}

.header-right {
    display: flex;
    align-items: center;
    gap: 16px;
}

#example-select {
    padding: 6px 12px;
    font-size: 0.875rem;
    background: var(--bg-tertiary);
    color: var(--text-primary);
    border: 1px solid var(--border-color);
    border-radius: 4px;
    cursor: pointer;
    min-width: 200px;
}

#example-select:focus {
    outline: none;
    border-color: var(--accent);
}

#example-select optgroup {
    color: var(--text-secondary);
}

.github-link {
    color: var(--text-secondary);
    transition: color 0.2s;
}

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

.nav-link {
    color: var(--text-secondary);
    text-decoration: none;
    font-size: 0.875rem;
    padding: 6px 12px;
    border-radius: 4px;
    transition: all 0.2s;
}

.nav-link:hover {
    color: var(--text-primary);
    background: var(--bg-tertiary);
}

/* Main layout */
main {
    display: flex;
    height: calc(100vh - var(--header-height));
}

.pane {
    display: flex;
    flex-direction: column;
    min-width: 200px;
}

.editor-pane {
    flex: 1;
    background: var(--bg-secondary);
}

.preview-pane {
    flex: 1;
    background: var(--bg-primary);
}

.pane-header {
    height: var(--pane-header-height);
    background: var(--bg-tertiary);
    border-bottom: 1px solid var(--border-color);
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 0 12px;
    font-size: 0.8125rem;
    color: var(--text-secondary);
}

.render-info {
    font-size: 0.75rem;
}

#render-time {
    color: var(--success-text);
}

/* Divider */
.divider {
    width: 4px;
    background: var(--border-color);
    cursor: col-resize;
    transition: background 0.2s;
}

.divider:hover,
.divider.dragging {
    background: var(--accent);
}

/* Editor */
#editor {
    flex: 1;
    width: 100%;
    padding: 16px;
    font-family: 'Fira Code', 'SF Mono', Menlo, Monaco, 'Courier New', monospace;
    font-size: 14px;
    line-height: 1.5;
    background: var(--bg-secondary);
    color: var(--text-primary);
    border: none;
    resize: none;
    outline: none;
    tab-size: 2;
}

#editor::placeholder {
    color: var(--text-secondary);
}

/* Preview */
#preview-container {
    flex: 1;
    overflow: auto;
    display: flex;
    align-items: center;
    justify-content: center;
    padding: 20px;
}

#preview {
    transform-origin: center center;
    transition: transform 0.1s ease-out;
}

#preview svg {
    max-width: 100%;
    height: auto;
    display: block;
}

.preview-actions {
    display: flex;
    gap: 4px;
}

.preview-actions button {
    padding: 4px 8px;
    font-size: 0.75rem;
    background: var(--bg-secondary);
    color: var(--text-primary);
    border: 1px solid var(--border-color);
    border-radius: 3px;
    cursor: pointer;
    transition: background 0.2s, border-color 0.2s;
}

.preview-actions button:hover {
    background: var(--bg-primary);
    border-color: var(--accent);
}

#download-svg {
    margin-left: 8px;
    background: var(--accent);
    border-color: var(--accent);
}

#download-svg:hover {
    background: var(--accent-hover);
    border-color: var(--accent-hover);
}

/* Error display */
#error-display {
    position: absolute;
    bottom: 0;
    left: 0;
    right: 0;
    padding: 12px 16px;
    background: var(--error-bg);
    color: var(--error-text);
    font-family: 'Fira Code', 'SF Mono', Menlo, monospace;
    font-size: 0.8125rem;
    line-height: 1.4;
    max-height: 150px;
    overflow-y: auto;
    border-top: 1px solid var(--error-text);
}

#error-display.hidden {
    display: none;
}

.preview-pane {
    position: relative;
}

/* Loading overlay */
#loading-overlay {
    position: fixed;
    inset: 0;
    background: rgba(0, 0, 0, 0.85);
    display: flex;
    align-items: center;
    justify-content: center;
    z-index: 1000;
}

#loading-overlay.hidden {
    display: none;
}

.loading-content {
    text-align: center;
}

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

.spinner {
    width: 40px;
    height: 40px;
    border: 3px solid var(--border-color);
    border-top-color: var(--accent);
    border-radius: 50%;
    animation: spin 1s linear infinite;
    margin: 0 auto;
}

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

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

    .divider {
        width: 100%;
        height: 4px;
        cursor: row-resize;
    }

    .pane {
        min-height: 200px;
    }

    .header-text {
        display: none;
    }

    .logo {
        height: 36px;
    }

    #example-select {
        min-width: 150px;
    }
}