:root {
    --bg: #1e1e1e;
    --surface: #252526;
    --surface2: #2d2d30;
    --border: #3e3e42;
    --text: #cccccc;
    --text-dim: #858585;
    --accent: #007acc;
    --accent-hover: #1a8fd1;
    --danger: #f44747;
    --sidebar-w: 18%;
    --header-h: 44px;
    --font: -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
    --mono: 'Cascadia Code', 'Fira Mono', 'Consolas', monospace;
}

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

html, body { height: 100%; overflow: hidden; background: var(--bg); color: var(--text); font-family: var(--font); font-size: clamp(12px, 1.2vw, 15px); }

/* ── Login ─────────────────────────────────────────────────────────────────── */
.login-body { display: flex; align-items: center; justify-content: center; height: 100vh; background: var(--bg); }
.login-card { background: var(--surface); border: 1px solid var(--border); border-radius: 8px; padding: clamp(24px, 4vw, 48px); width: clamp(260px, 30vw, 400px); display: flex; flex-direction: column; gap: 16px; }
.login-title { font-size: clamp(18px, 2vw, 24px); font-weight: 600; text-align: center; color: var(--text); }
.login-error { color: var(--danger); font-size: 0.875em; text-align: center; }
.login-form { display: flex; flex-direction: column; gap: 10px; }
.login-form label { font-size: 0.85em; color: var(--text-dim); }
.login-form input[type="password"] { background: var(--bg); border: 1px solid var(--border); border-radius: 4px; padding: 8px 10px; color: var(--text); font-size: 1em; outline: none; }
.login-form input[type="password"]:focus { border-color: var(--accent); }

/* ── Header ─────────────────────────────────────────────────────────────────── */
.app-header { height: var(--header-h); background: var(--surface); border-bottom: 1px solid var(--border); display: flex; align-items: center; padding: 0 12px; gap: 10px; position: fixed; top: 0; left: 0; right: 0; z-index: 100; }
.app-title { flex: 1; font-weight: 600; font-size: clamp(13px, 1.4vw, 16px); color: var(--text); }
.header-actions { display: flex; align-items: center; gap: 8px; }

/* ── Shell ──────────────────────────────────────────────────────────────────── */
.shell { display: flex; position: fixed; top: var(--header-h); left: 0; right: 0; bottom: 0; }

/* ── Sidebar ────────────────────────────────────────────────────────────────── */
.sidebar { width: var(--sidebar-w); min-width: 180px; max-width: 300px; background: var(--surface); border-right: 1px solid var(--border); display: flex; flex-direction: column; overflow: hidden; transition: width 0.2s ease, min-width 0.2s ease; flex-shrink: 0; }
.sidebar.collapsed { width: 0; min-width: 0; }
.sidebar-top { padding: 10px 8px; border-bottom: 1px solid var(--border); }
.notebook-list { flex: 1; overflow-y: auto; padding: 6px 0; }
.sidebar-loading { padding: 12px; color: var(--text-dim); font-size: 0.85em; }

/* Notebooks */
.nb-section { }
.nb-header { display: flex; align-items: center; gap: 4px; padding: 5px 8px; cursor: pointer; user-select: none; }
.nb-header:hover { background: var(--surface2); }
.nb-toggle { color: var(--text-dim); font-size: 0.7em; width: 14px; flex-shrink: 0; transition: transform 0.15s; }
.nb-toggle.open { transform: rotate(90deg); }
.nb-name { flex: 1; font-size: 0.88em; white-space: nowrap; overflow: hidden; text-overflow: ellipsis; }
.nb-name-input { flex: 1; background: var(--bg); border: 1px solid var(--accent); border-radius: 3px; color: var(--text); font-size: 0.88em; padding: 1px 4px; }
.nb-actions { display: flex; gap: 2px; opacity: 0; transition: opacity 0.1s; }
.nb-header:hover .nb-actions { opacity: 1; }
.nb-pages { padding-left: 14px; }
.nb-pages.hidden { display: none; }

/* Pages */
.page-item { display: flex; align-items: center; gap: 4px; padding: 4px 8px; cursor: pointer; border-radius: 3px; }
.page-item:hover { background: var(--surface2); }
.page-item.active { background: var(--accent); color: #fff; }
.page-item.active .page-type-badge { color: rgba(255,255,255,0.7); }
.page-name { flex: 1; font-size: 0.84em; white-space: nowrap; overflow: hidden; text-overflow: ellipsis; }
.page-name-input { flex: 1; background: var(--bg); border: 1px solid var(--accent); border-radius: 3px; color: var(--text); font-size: 0.84em; padding: 1px 4px; }
.page-type-badge { font-size: 0.7em; color: var(--text-dim); flex-shrink: 0; }
.page-actions { display: flex; gap: 2px; opacity: 0; transition: opacity 0.1s; }
.page-item:hover .page-actions { opacity: 1; }
.page-item.active .page-actions { opacity: 1; }

.add-page-row { padding: 3px 8px 3px 22px; }
.btn-add-page { background: none; border: none; color: var(--text-dim); font-size: 0.8em; cursor: pointer; padding: 2px 6px; border-radius: 3px; }
.btn-add-page:hover { color: var(--text); background: var(--surface2); }

/* ── Buttons ────────────────────────────────────────────────────────────────── */
.btn-primary { background: var(--accent); color: #fff; border: none; border-radius: 4px; padding: 6px 14px; font-size: 0.85em; cursor: pointer; font-family: var(--font); }
.btn-primary:hover { background: var(--accent-hover); }
.btn-text { background: none; border: none; color: var(--text-dim); font-size: 0.85em; cursor: pointer; padding: 4px 8px; border-radius: 3px; font-family: var(--font); }
.btn-text:hover { color: var(--text); background: var(--surface2); }
.btn-icon { background: none; border: none; color: var(--text-dim); font-size: 1.1em; cursor: pointer; width: 30px; height: 30px; display: inline-flex; align-items: center; justify-content: center; border-radius: 4px; text-decoration: none; }
.btn-icon:hover { color: var(--text); background: var(--surface2); }
.btn-new-notebook { width: 100%; font-size: 0.82em; padding: 6px 8px; }

.btn-danger { background: none; border: none; color: var(--danger); cursor: pointer; font-size: 0.8em; padding: 2px 4px; border-radius: 3px; opacity: 0.7; }
.btn-danger:hover { opacity: 1; background: rgba(244,71,71,0.1); }

/* ── Editor Area ────────────────────────────────────────────────────────────── */
.editor-area { flex: 1; overflow: hidden; display: flex; flex-direction: column; }

/* Empty state */
.empty-state { display: flex; flex-direction: column; align-items: center; justify-content: center; height: 100%; gap: 10px; color: var(--text-dim); }

/* Text editor */
.text-editor-wrap { display: flex; flex-direction: column; height: 100%; }
.editor-toolbar { display: flex; align-items: center; gap: 12px; padding: 6px 12px; border-bottom: 1px solid var(--border); background: var(--surface); }
.page-name-display { font-size: 0.9em; color: var(--text-dim); }
.save-indicator { font-size: 0.8em; color: var(--text-dim); margin-left: auto; }
.save-indicator.saving { color: var(--accent); }
.save-indicator.saved { color: #4ec9b0; }
.save-indicator.error { color: var(--danger); }
.text-editor { flex: 1; background: var(--bg); color: var(--text); font-family: var(--mono); font-size: clamp(12px, 1.3vw, 15px); line-height: 1.6; border: none; outline: none; resize: none; padding: clamp(16px, 2vw, 32px) clamp(20px, 4vw, 64px); }

/* Canvas editor */
.canvas-editor-wrap { display: flex; flex-direction: column; height: 100%; }
.canvas-toolbar { display: flex; align-items: center; gap: 8px; padding: 6px 10px; background: var(--surface); border-bottom: 1px solid var(--border); flex-wrap: wrap; flex-shrink: 0; position: relative; z-index: 10; }
.tool-groups { display: flex; gap: 4px; }
.tool-group { position: relative; }
.group-toggle { background: var(--surface2); border: 1px solid var(--border); color: var(--text); padding: 4px 8px; border-radius: 4px; cursor: pointer; font-size: 0.78em; white-space: nowrap; }
.group-toggle:hover, .group-toggle.open { background: var(--accent); color: #fff; border-color: var(--accent); }
.group-panel { position: absolute; top: calc(100% + 4px); left: 0; background: var(--surface2); border: 1px solid var(--border); border-radius: 4px; padding: 6px; display: flex; flex-direction: column; gap: 4px; z-index: 200; min-width: 90px; }
.group-panel.hidden { display: none; }

.tool-btn { background: none; border: 1px solid transparent; color: var(--text); padding: 5px 10px; border-radius: 4px; cursor: pointer; font-size: 1em; text-align: left; white-space: nowrap; }
.tool-btn:hover { background: var(--surface); border-color: var(--border); }
.tool-btn.active { background: var(--accent); color: #fff; border-color: var(--accent); }

.tool-sizes { display: flex; align-items: center; gap: 4px; border-left: 1px solid var(--border); padding-left: 8px; }
.tool-label { font-size: 0.75em; color: var(--text-dim); }
.size-btn { background: var(--surface2); border: 1px solid var(--border); color: var(--text); width: 28px; height: 28px; border-radius: 4px; cursor: pointer; font-size: 0.78em; }
.size-btn:hover { border-color: var(--accent); }
.size-btn.active { background: var(--accent); color: #fff; border-color: var(--accent); }

.color-section { display: flex; align-items: center; gap: 6px; border-left: 1px solid var(--border); padding-left: 8px; }
.color-swatches { display: grid; grid-template-columns: repeat(8, 18px); gap: 2px; }
.color-swatch { width: 18px; height: 18px; border-radius: 3px; cursor: pointer; border: 2px solid transparent; }
.color-swatch:hover { border-color: #fff; }
.color-swatch.selected-fg { border-color: #fff; }
.color-current { position: relative; width: 34px; height: 34px; }
.swatch-bg { position: absolute; width: 22px; height: 22px; bottom: 0; right: 0; border-radius: 3px; border: 2px solid var(--border); cursor: pointer; }
.swatch-fg { position: absolute; width: 22px; height: 22px; top: 0; left: 0; border-radius: 3px; border: 2px solid #fff; cursor: pointer; z-index: 1; }

.canvas-actions { display: flex; align-items: center; gap: 8px; margin-left: auto; }
.canvas-viewport { flex: 1; overflow: hidden; display: flex; align-items: center; justify-content: center; background: #404040; position: relative; cursor: crosshair; isolation: isolate; }
#canvasInner { position: relative; flex-shrink: 0; line-height: 0; transform-origin: center center; }
#canvasLoadingOverlay { position: absolute; inset: 0; z-index: 20; display: flex; flex-direction: column; align-items: center; justify-content: center; gap: 12px; background: rgba(30,30,30,0.82); color: #ccc; font-size: 0.9em; pointer-events: none; }
#canvasLoadingOverlay.hidden { display: none; }
.loading-spinner { width: 32px; height: 32px; border: 3px solid #444; border-top-color: var(--accent); border-radius: 50%; animation: spin 0.75s linear infinite; }
@keyframes spin { to { transform: rotate(360deg); } }
#linesCanvas { position: absolute; top: 0; left: 0; z-index: 0; pointer-events: none; }
#mainCanvas { position: relative; z-index: 1; box-shadow: 0 0 20px rgba(0,0,0,0.5); cursor: crosshair; touch-action: none; display: block; }

/* ── Settings ────────────────────────────────────────────────────────────────── */
.settings-wrap { padding: clamp(20px, 3vw, 48px); max-width: 600px; overflow-y: auto; height: 100%; }
.settings-wrap h2 { margin-bottom: 24px; font-size: clamp(16px, 1.8vw, 22px); }
.settings-section { margin-bottom: 32px; }
.settings-section h3 { font-size: 0.95em; margin-bottom: 8px; color: var(--text); border-bottom: 1px solid var(--border); padding-bottom: 6px; }
.settings-hint { font-size: 0.8em; color: var(--text-dim); margin-bottom: 12px; }
.canvas-size-options { display: flex; flex-direction: column; gap: 8px; }
.size-option { display: flex; align-items: center; gap: 10px; padding: 8px 12px; background: var(--surface); border: 1px solid var(--border); border-radius: 6px; cursor: pointer; }
.size-option:hover { border-color: var(--accent); }
.size-option input[type="radio"] { accent-color: var(--accent); }
.size-option em { color: var(--text-dim); font-size: 0.85em; margin-left: 6px; font-style: normal; }
.settings-select { background: var(--surface2); border: 1px solid var(--border); color: var(--text); padding: 6px 10px; border-radius: 4px; font-size: 0.9em; }
.settings-actions { display: flex; align-items: center; gap: 12px; }

/* ── Modal ──────────────────────────────────────────────────────────────────── */
.modal-overlay { position: fixed; inset: 0; background: rgba(0,0,0,0.6); display: flex; align-items: center; justify-content: center; z-index: 1000; }
.modal-overlay.hidden { display: none; }
.modal { background: var(--surface); border: 1px solid var(--border); border-radius: 8px; padding: 24px; width: clamp(260px, 30vw, 400px); display: flex; flex-direction: column; gap: 14px; }
#modalMessage { font-size: 0.95em; }
.modal-input { background: var(--bg); border: 1px solid var(--border); color: var(--text); border-radius: 4px; padding: 8px 10px; font-size: 0.95em; outline: none; }
.modal-input:focus { border-color: var(--accent); }
.modal-actions { display: flex; gap: 8px; justify-content: flex-end; }

/* ── Add-page inline form ───────────────────────────────────────────────────── */
.add-page-form { padding: 6px 8px 6px 22px; display: flex; flex-direction: column; gap: 6px; }
.add-page-form input[type="text"] { background: var(--bg); border: 1px solid var(--border); color: var(--text); border-radius: 3px; padding: 4px 6px; font-size: 0.82em; }
.add-page-form select { background: var(--bg); border: 1px solid var(--border); color: var(--text); border-radius: 3px; padding: 4px 6px; font-size: 0.82em; }
.add-page-style-select { background: var(--bg); border: 1px solid var(--border); color: var(--text); border-radius: 3px; padding: 4px 6px; font-size: 0.8em; width: 100%; }
.add-page-form-actions { display: flex; gap: 4px; }
.btn-type { background: var(--surface2); border: 1px solid var(--border); color: var(--text-dim); font-size: 0.78em; padding: 3px 10px; border-radius: 4px; cursor: pointer; font-family: var(--font); font-weight: 600; letter-spacing: 0.04em; }
.btn-type:hover { border-color: var(--accent); color: var(--text); }
.btn-type.active { background: var(--accent); border-color: var(--accent); color: #fff; }

/* ── Responsive ─────────────────────────────────────────────────────────────── */
@media (max-width: 1023px) {
    :root { --sidebar-w: 220px; }
    .sidebar { position: fixed; top: var(--header-h); left: 0; bottom: 0; z-index: 50; box-shadow: 4px 0 12px rgba(0,0,0,0.4); }
    .sidebar.collapsed { width: 0; min-width: 0; }
    .editor-area { margin-left: 0; }
}
@media (max-width: 767px) {
    .color-swatches { grid-template-columns: repeat(8, 16px); }
    .color-swatch { width: 16px; height: 16px; }
    .canvas-toolbar { gap: 4px; padding: 4px 6px; }
}