/* ─── Dark Mode (default) ──────────────────────────────────────────────── */
:root,
[data-mode="dark"] {
    --bg: #0c0c14;
    --panel: #12121c;
    --panel-raised: #1a1a28;
    --panel-grad: #0a0a16;
    --border: #2a2a3e;
    --border-subtle: #1e1e30;
    --accent: #6366f1;
    --accent-hover: #818cf8;
    --accent-muted: rgba(99,102,241,0.15);
    --red: #f87171;
    --green: #4ade80;
    --blue: #60a5fa;
    --text: #e2e4f0;
    --text-secondary: #8b8da8;
    --text-muted: #505072;
    --toggle-off: #3a3a50;
    --overlay-bg: rgba(12,12,20,0.75);
    --overlay-heavy: rgba(12,12,20,0.9);
    --kbd-bg: rgba(30,30,56,0.8);
    --swatch-ring: rgba(255,255,255,0.85);

    /* Layout & Sizing (overridable for mobile) */
    --panel-width: 280px;
    --panel-padding: 20px;
    --btn-sm: 28px;
    --btn-xs: 24px;
    --input-size: 40px;
    --toggle-w: 36px;
    --toggle-h: 20px;
    --draw-canvas-size: 120px;
    --preview-canvas-size: 48px;
    --gap-md: 8px;
    --gap-sm: 4px;
}

/* ─── Light Mode ───────────────────────────────────────────────────────── */
[data-mode="light"] {
    --bg: #f5f5f9;
    --panel: #ffffff;
    --panel-raised: #f0f0f6;
    --panel-grad: #eaeaf2;
    --border: #dcdce8;
    --border-subtle: #e8e8f0;
    --accent: #4f46e5;
    --accent-hover: #6366f1;
    --accent-muted: rgba(79,70,229,0.08);
    --red: #ef4444;
    --green: #22c55e;
    --blue: #3b82f6;
    --text: #1a1a2e;
    --text-secondary: #6b6b88;
    --text-muted: #9b9bb8;
    --toggle-off: #c8c8d8;
    --overlay-bg: rgba(245,245,249,0.8);
    --overlay-heavy: rgba(245,245,249,0.92);
    --kbd-bg: rgba(220,220,232,0.8);
    --swatch-ring: var(--accent);
}

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

html {
    -webkit-text-size-adjust: 100%;
    text-size-adjust: 100%;
}

body {
    background: var(--bg);
    color: var(--text);
    font-family: 'Space Mono', monospace;
    display: flex;
    height: 100dvh;
    overflow: hidden;
}

/* ═══ PANEL ════════════════════════════════════════════════════════════════ */
#panel {
    width: var(--panel-width);
    min-width: var(--panel-width);
    background: var(--panel);
    border-right: 1px solid var(--border);
    display: flex;
    flex-direction: column;
    overflow: hidden;
}

/* ─── Panel Header ─────────────────────────────────────────────────────── */
.panel-header {
    padding: 16px var(--panel-padding) 14px;
    border-bottom: 1px solid var(--border);
    background: linear-gradient(180deg, var(--panel-grad) 0%, var(--panel) 100%);
    display: flex;
    align-items: center;
    justify-content: space-between;
    flex-shrink: 0;
}

.panel-header-brand {
    display: flex;
    flex-direction: column;
    align-items: center;
    flex: 1;
}

.logo {
    font-family: 'Orbitron', sans-serif;
    font-size: 24px;
    font-weight: 900;
    letter-spacing: 8px;
    text-indent: 8px;
    background: linear-gradient(135deg, var(--accent-hover), var(--blue));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
}

.tagline {
    font-size: 8px;
    color: var(--text-muted);
    letter-spacing: 3px;
    margin-top: 2px;
    text-transform: uppercase;
    text-indent: 3px;
}

/* ─── Light/Dark Toggle Button ─────────────────────────────────────────── */
.mode-toggle-btn {
    width: 32px;
    height: 32px;
    border-radius: 8px;
    border: 1px solid var(--border);
    background: var(--panel-raised);
    color: var(--text-secondary);
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: all 0.2s;
    flex-shrink: 0;
    margin-top: 2px;
}
.lang-label {
    font-family: 'Space Mono', monospace;
    font-size: 11px;
    font-weight: 700;
    line-height: 1;
}
.mode-toggle-btn:hover {
    border-color: var(--accent);
    color: var(--accent);
    background: var(--accent-muted);
}

.mode-icon {
    width: 18px;
    height: 18px;
    stroke-linecap: round;
    stroke-linejoin: round;
}

/* Show sun in dark mode, moon in light mode */
[data-mode="dark"] .mode-icon-sun { display: block; }
[data-mode="dark"] .mode-icon-moon { display: none; }
[data-mode="light"] .mode-icon-sun { display: none; }
[data-mode="light"] .mode-icon-moon { display: block; }

/* ─── Scrollable Area ──────────────────────────────────────────────────── */
.panel-scroll {
    flex: 1;
    overflow-y: auto;
    overflow-x: hidden;
    scrollbar-width: thin;
    scrollbar-color: var(--text-muted) transparent;
}

/* ═══ COLLAPSIBLE SECTIONS ═════════════════════════════════════════════════ */
.panel-section {
    border-bottom: 1px solid var(--border);
}

.section-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 12px var(--panel-padding);
    cursor: pointer;
    user-select: none;
    transition: background 0.15s;
}
.section-header:hover {
    background: var(--accent-muted);
}

.section-label-group {
    display: flex;
    align-items: baseline;
    gap: var(--gap-md);
}

.section-label {
    font-size: 10px;
    letter-spacing: 2px;
    text-transform: uppercase;
    color: var(--text-muted);
    font-weight: 700;
}

.section-label-en {
    font-size: 8px;
    letter-spacing: 1.5px;
    color: var(--text-muted);
    opacity: 0.5;
    text-transform: uppercase;
}

/* Chevron */
.section-chevron {
    width: 16px;
    height: 16px;
    display: flex;
    align-items: center;
    justify-content: center;
    flex-shrink: 0;
    transition: transform 0.25s cubic-bezier(0.4, 0, 0.2, 1);
}
.section-chevron::after {
    content: '';
    width: 6px;
    height: 6px;
    border-right: 1.5px solid var(--text-muted);
    border-bottom: 1.5px solid var(--text-muted);
    transform: rotate(45deg);
    margin-top: -3px;
    transition: transform 0.25s cubic-bezier(0.4, 0, 0.2, 1);
}

/* Collapsible body using grid trick */
.section-body {
    display: grid;
    grid-template-rows: 1fr;
    transition: grid-template-rows 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

.section-content {
    overflow: hidden;
    padding: 0 var(--panel-padding) 16px;
}

/* Collapsed state */
.panel-section.collapsed .section-body {
    grid-template-rows: 0fr;
}
.panel-section.collapsed .section-content {
    padding-bottom: 0;
}
.panel-section.collapsed .section-chevron {
    transform: rotate(-90deg);
}

/* ═══ LETTER INPUTS ════════════════════════════════════════════════════════ */
.letter-row {
    display: flex;
    align-items: center;
    gap: var(--gap-md);
    margin-bottom: 10px;
}
.letter-row:last-child { margin-bottom: 0; }

.axis-tag {
    width: 30px;
    height: 30px;
    border-radius: 6px;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 9px;
    font-weight: 700;
    letter-spacing: 1px;
    flex-shrink: 0;
}
.ax-r { background: rgba(248,113,113,0.12); color: var(--red); border: 1px solid rgba(248,113,113,0.25); }
.ax-g { background: rgba(74,222,128,0.12); color: var(--green); border: 1px solid rgba(74,222,128,0.25); }
.ax-b { background: rgba(96,165,250,0.12); color: var(--blue); border: 1px solid rgba(96,165,250,0.25); }

.letter-input {
    width: var(--input-size);
    height: var(--input-size);
    background: var(--bg);
    border: 1.5px solid var(--border);
    border-radius: 8px;
    color: var(--text);
    font-family: 'Orbitron', "Noto Sans TC", "PingFang TC", "Microsoft JhengHei", sans-serif;
    font-size: 18px;
    font-weight: 700;
    text-align: center;
    outline: none;
    transition: border-color 0.2s, box-shadow 0.2s;
    flex-shrink: 0;
}
.letter-input.over-limit { border-color: #ef4444 !important; box-shadow: 0 0 0 3px rgba(239,68,68,0.25) !important; }

/* ─── Shape Mode ─────────────────────────────────────────────────────── */
.proj-mode-tabs { margin-bottom: 12px; }
.shape-row {
    display: flex;
    align-items: flex-start;
    gap: var(--gap-md);
    margin-bottom: 10px;
}
.shape-row:last-child { margin-bottom: 0; }
.shape-selector {
    display: flex;
    gap: var(--gap-sm);
    flex-wrap: wrap;
    flex: 1;
    min-width: 0;
}
.shape-btn {
    width: var(--btn-sm);
    height: var(--btn-sm);
    border-radius: 6px;
    border: 1.5px solid var(--border);
    background: var(--bg);
    color: var(--text-secondary);
    font-size: 14px;
    line-height: 1;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: all 0.15s ease;
    padding: 0;
}
.shape-btn:hover {
    border-color: var(--accent);
    color: var(--text);
    background: var(--accent-muted);
}
.shape-btn.active {
    border-color: var(--accent);
    background: var(--accent);
    color: #fff;
}
[data-axis="x"] .shape-btn.active { border-color: var(--red); background: rgba(248,113,113,0.25); color: var(--red); }
[data-axis="z"] .shape-btn.active { border-color: var(--green); background: rgba(74,222,128,0.25); color: var(--green); }
[data-axis="y"] .shape-btn.active { border-color: var(--blue); background: rgba(96,165,250,0.25); color: var(--blue); }

/* ─── Draw Mode ──────────────────────────────────────────────────────── */
.draw-row {
    display: flex;
    align-items: flex-start;
    gap: var(--gap-md);
    margin-bottom: 10px;
}
.draw-row:last-child { margin-bottom: 0; }
.draw-canvas {
    width: var(--draw-canvas-size);
    height: var(--draw-canvas-size);
    border-radius: 6px;
    cursor: crosshair;
    image-rendering: pixelated;
    background: var(--bg);
    flex-shrink: 0;
}
#drawX { border: 1.5px solid rgba(248,113,113,0.3); }
#drawZ { border: 1.5px solid rgba(74,222,128,0.3); }
#drawY { border: 1.5px solid rgba(96,165,250,0.3); }
.draw-tools {
    display: flex;
    flex-direction: column;
    gap: var(--gap-sm);
}
.draw-tool-btn {
    width: var(--btn-sm);
    height: var(--btn-sm);
    border-radius: 6px;
    border: 1.5px solid var(--border);
    background: var(--bg);
    color: var(--text-secondary);
    font-size: 14px;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: all 0.15s ease;
    padding: 0;
}
.draw-tool-btn:hover {
    border-color: var(--accent);
    color: var(--text);
}
.draw-tool-btn.active {
    border-color: var(--accent);
    background: var(--accent);
    color: #fff;
}
.letter-input:focus { border-color: var(--accent-hover); box-shadow: 0 0 0 3px var(--accent-muted); }
.letter-input.ri:focus { border-color: var(--red); box-shadow: 0 0 0 3px rgba(248,113,113,0.15); }
.letter-input.gi:focus { border-color: var(--green); box-shadow: 0 0 0 3px rgba(74,222,128,0.15); }
.letter-input.bi:focus { border-color: var(--blue); box-shadow: 0 0 0 3px rgba(96,165,250,0.15); }

.preview-canvas {
    width: var(--preview-canvas-size);
    height: var(--preview-canvas-size);
    border-radius: 6px;
    flex-shrink: 0;
}
#pvX { border: 1px solid rgba(248,113,113,0.2); }
#pvZ { border: 1px solid rgba(74,222,128,0.2); }
#pvY { border: 1px solid rgba(96,165,250,0.2); }

.axis-desc {
    font-size: 9px;
    color: var(--text-muted);
    line-height: 1.4;
    flex-shrink: 0;
}

/* ═══ GENERATE BUTTON ══════════════════════════════════════════════════════ */
/* ═══ GENERATE BUTTON ═════════════════════════════════════════════════════ */
.btn-gen {
    display: block;
    margin: 12px 20px;
    padding: 0;
    width: calc(100% - 40px);
    height: 44px;
    background: linear-gradient(135deg, var(--accent), #8b5cf6);
    border: none;
    border-radius: 10px;
    color: #fff;
    font-family: 'Space Mono', monospace;
    font-size: 12px;
    font-weight: 700;
    letter-spacing: 2px;
    cursor: pointer;
    transition: all 0.2s cubic-bezier(0.4, 0, 0.2, 1);
    text-transform: uppercase;
    text-align: center;
    flex-shrink: 0;
}
.btn-gen:hover {
    transform: translateY(-1px);
    box-shadow: 0 6px 24px rgba(99,102,241,0.35);
}
.btn-gen:active {
    transform: translateY(0);
    box-shadow: 0 2px 8px rgba(99,102,241,0.2);
}

/* ═══ SLIDERS ══════════════════════════════════════════════════════════════ */
.slider-row {
    display: flex;
    align-items: center;
    gap: var(--gap-md);
    margin-bottom: 10px;
}
.slider-row:last-of-type { margin-bottom: 0; }

.slider-label {
    font-size: 11px;
    min-width: 56px;
    color: var(--text-secondary);
}
.slider-val {
    font-size: 10px;
    font-weight: 700;
    color: var(--accent);
    background: var(--accent-muted);
    border-radius: 10px;
    padding: 2px 8px;
    min-width: 32px;
    text-align: center;
}

input[type="range"] {
    flex: 1;
    -webkit-appearance: none;
    height: 3px;
    background: var(--border);
    border-radius: 2px;
    outline: none;
}
input[type="range"]::-webkit-slider-thumb {
    -webkit-appearance: none;
    width: 16px;
    height: 16px;
    background: var(--accent);
    border-radius: 50%;
    cursor: pointer;
    border: 2px solid var(--panel);
    box-shadow: 0 1px 4px rgba(0,0,0,0.2);
    transition: transform 0.15s;
}
input[type="range"]::-webkit-slider-thumb:hover {
    transform: scale(1.15);
}
input[type="range"]::-moz-range-thumb {
    width: 16px;
    height: 16px;
    background: var(--accent);
    border-radius: 50%;
    cursor: pointer;
    border: 2px solid var(--panel);
    box-shadow: 0 1px 4px rgba(0,0,0,0.2);
}

.sub-label {
    font-size: 9px;
    letter-spacing: 1.5px;
    text-transform: uppercase;
    color: var(--text-muted);
    margin: 12px 0 8px;
}

/* ═══ TOGGLES ══════════════════════════════════════════════════════════════ */
.toggle-row {
    display: flex;
    align-items: center;
    justify-content: space-between;
    margin-bottom: 8px;
}
.toggle-row:last-child { margin-bottom: 0; }
.toggle-label { font-size: 11px; color: var(--text-secondary); }

.toggle {
    width: var(--toggle-w);
    height: var(--toggle-h);
    border-radius: 10px;
    background: var(--border);
    cursor: pointer;
    position: relative;
    transition: background 0.25s cubic-bezier(0.4, 0, 0.2, 1);
    flex-shrink: 0;
}
.toggle::after {
    content: '';
    position: absolute;
    top: 2px;
    left: 2px;
    width: 16px;
    height: 16px;
    border-radius: 50%;
    background: var(--toggle-off);
    transition: all 0.25s cubic-bezier(0.4, 0, 0.2, 1);
    box-shadow: 0 1px 3px rgba(0,0,0,0.15);
}
.toggle.on { background: var(--accent); }
.toggle.on::after {
    left: 18px;
    background: #fff;
}

/* ═══ ALGORITHM SELECTOR (Segmented Control) ═══════════════════════════════ */
.algo-select {
    display: flex;
    gap: 2px;
    background: var(--bg);
    border: 1px solid var(--border);
    border-radius: 8px;
    padding: 2px;
}
.algo-option {
    flex: 1;
    display: flex;
    align-items: center;
    justify-content: center;
    cursor: pointer;
}
.algo-option input[type="radio"] {
    display: none;
}
.algo-option span {
    display: block;
    width: 100%;
    padding: 6px 2px;
    text-align: center;
    font-size: 10px;
    color: var(--text-secondary);
    background: transparent;
    border: none;
    border-radius: 6px;
    transition: all 0.2s;
}
.algo-option input[type="radio"]:checked + span {
    background: var(--accent);
    color: #fff;
}
.algo-option:hover span {
    color: var(--text);
    background: var(--accent-muted);
}
.algo-option:has(input[type="radio"]:checked):hover span {
    background: var(--accent);
    color: #fff;
}

/* Algorithm description (shows active only) */
.algo-desc {
    margin-top: 8px;
    padding: 8px 10px;
    background: var(--panel-raised);
    border: 1px solid var(--border-subtle);
    border-radius: 6px;
}
.algo-desc p {
    margin: 0;
    font-size: 11px;
    color: var(--text-secondary);
    line-height: 1.5;
}

/* Info tooltip (uses native title attribute) */
.info-tip {
    width: 14px;
    height: 14px;
    border-radius: 50%;
    background: var(--border);
    color: var(--text-muted);
    font-size: 9px;
    font-weight: 700;
    display: inline-flex;
    align-items: center;
    justify-content: center;
    cursor: help;
    margin-left: 4px;
    vertical-align: middle;
    flex-shrink: 0;
}

/* Progress bar */
.progress-bar {
    height: 3px;
    background: var(--border);
    border-radius: 2px;
    overflow: hidden;
}
.progress-fill {
    height: 100%;
    width: 0%;
    background: linear-gradient(90deg, var(--accent), var(--accent-hover));
    border-radius: 2px;
    transition: width 0.3s ease;
}
.progress-text {
    font-size: 9px;
    color: var(--text-muted);
    text-align: center;
    margin-top: 4px;
}

/* ═══ SEGMENTED CONTROL (Mode Buttons) ═════════════════════════════════════ */
.seg-control {
    display: flex;
    gap: 2px;
    background: var(--bg);
    border: 1px solid var(--border);
    border-radius: 8px;
    padding: 2px;
}
.seg-btn {
    flex: 1;
    padding: 8px 4px;
    background: transparent;
    border: none;
    border-radius: 6px;
    color: var(--text-secondary);
    font-family: 'Space Mono', monospace;
    font-size: 10px;
    cursor: pointer;
    transition: all 0.2s;
    white-space: nowrap;
}
.seg-btn.active {
    background: var(--accent);
    color: #fff;
}
.seg-btn:hover:not(.active) {
    background: var(--accent-muted);
    color: var(--text);
}
.seg-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
}

/* ═══ STATS ════════════════════════════════════════════════════════════════ */
.stats-grid {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 6px;
}
.stat-card {
    background: var(--panel-raised);
    border: 1px solid var(--border-subtle);
    border-radius: 8px;
    padding: 10px 8px 8px;
    text-align: center;
    border-left: 3px solid var(--border);
}
.sc-indigo { border-left-color: #6366f1; }
.sc-blue   { border-left-color: #60a5fa; }
.sc-green  { border-left-color: #4ade80; }
.sc-orange { border-left-color: #f97316; }

.sv {
    font-family: 'Orbitron', sans-serif;
    font-size: 18px;
    font-weight: 700;
    color: var(--accent-hover);
}
.sl {
    font-size: 8px;
    color: var(--text-muted);
    letter-spacing: 1px;
    margin-top: 2px;
    text-transform: uppercase;
}

/* ═══ STYLE / COLOR SETTINGS ═══════════════════════════════════════════════ */
.style-group {
    margin-bottom: 14px;
}
.style-group:last-child { margin-bottom: 0; }

.style-label {
    font-size: 10px;
    color: var(--text-secondary);
    margin-bottom: 8px;
    display: block;
}

.swatch-row {
    display: flex;
    gap: var(--gap-md);
    align-items: center;
}

.swatch {
    width: var(--btn-xs);
    height: var(--btn-xs);
    border-radius: 50%;
    border: 2px solid transparent;
    cursor: pointer;
    transition: all 0.15s ease;
    outline: none;
    padding: 0;
    box-shadow: inset 0 0 0 1px rgba(255,255,255,0.08);
    flex-shrink: 0;
}
.swatch:hover {
    transform: scale(1.12);
}
.swatch.active {
    border-color: var(--swatch-ring);
    box-shadow: 0 0 0 2px var(--accent-muted), inset 0 0 0 1px rgba(255,255,255,0.12);
}

.color-row {
    display: flex;
    align-items: center;
    gap: var(--gap-md);
    margin-bottom: 8px;
}
.color-row:last-child { margin-bottom: 0; }

.color-axis {
    width: 22px;
    height: 22px;
    border-radius: 4px;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 8px;
    font-weight: 700;
    flex-shrink: 0;
}

/* Color picker input styled as + circle */
.swatch-picker {
    width: 24px;
    height: 24px;
    border-radius: 50%;
    border: 2px dashed var(--border);
    cursor: pointer;
    padding: 0;
    background: var(--panel-raised);
    -webkit-appearance: none;
    -moz-appearance: none;
    appearance: none;
    transition: all 0.15s ease;
    flex-shrink: 0;
}
.swatch-picker:hover {
    transform: scale(1.12);
    border-color: var(--accent);
}
.swatch-picker::-webkit-color-swatch-wrapper {
    padding: 0;
}
.swatch-picker::-webkit-color-swatch {
    border: none;
    border-radius: 50%;
    opacity: 0;
}
.swatch-picker::-moz-color-swatch {
    border: none;
    border-radius: 50%;
    opacity: 0;
}
.swatch-picker.active {
    border-style: solid;
    border-color: var(--swatch-ring);
    box-shadow: 0 0 0 2px var(--accent-muted);
}
.swatch-picker.active::-webkit-color-swatch {
    opacity: 1;
}
.swatch-picker.active::-moz-color-swatch {
    opacity: 1;
}

/* ═══ EXPORT GRID ══════════════════════════════════════════════════════════ */
.export-grid {
    display: grid;
    grid-template-columns: 1fr 1fr 1fr;
    gap: 6px;
}
.export-btn {
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    gap: 2px;
    padding: 10px 4px 8px;
    background: var(--panel-raised);
    border: 1px solid var(--border-subtle);
    border-radius: 8px;
    cursor: pointer;
    transition: all 0.2s;
    color: var(--text);
    font-family: 'Space Mono', monospace;
}
.export-btn:hover {
    border-color: var(--accent);
    background: var(--accent-muted);
    transform: translateY(-1px);
    box-shadow: 0 3px 12px rgba(99,102,241,0.15);
}
.export-btn:active {
    transform: translateY(0);
}
.export-btn.exporting {
    opacity: 0.5;
    pointer-events: none;
}
.export-icon {
    font-size: 18px;
    line-height: 1;
}
.export-name {
    font-size: 10px;
    font-weight: 700;
    letter-spacing: 1px;
    color: var(--accent-hover);
}
.export-desc {
    font-size: 8px;
    color: var(--text-muted);
    letter-spacing: 0.5px;
}

/* Import row */
.import-row {
    margin-top: 10px;
    padding-top: 10px;
    border-top: 1px solid var(--border-subtle);
}
.import-btn {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 6px;
    width: 100%;
    padding: 8px 12px;
    background: transparent;
    border: 1px dashed var(--border);
    border-radius: 8px;
    color: var(--text-secondary);
    font-family: 'Space Mono', monospace;
    font-size: 10px;
    letter-spacing: 1px;
    cursor: pointer;
    transition: all 0.2s;
}
.import-btn:hover {
    border-color: var(--accent);
    color: var(--accent);
    background: var(--accent-muted);
}
.import-icon {
    font-size: 14px;
}

/* ═══ ABOUT SECTION ════════════════════════════════════════════════════════ */
.about-content {
    padding-bottom: 24px;
}
.about-block {
    margin-bottom: 14px;
}
.about-block:last-child {
    margin-bottom: 0;
}
.about-heading {
    font-size: 9px;
    font-weight: 700;
    letter-spacing: 1.5px;
    color: var(--accent-hover);
    margin-bottom: 6px;
    padding-bottom: 4px;
    border-bottom: 1px solid var(--border-subtle);
}
.about-item {
    display: flex;
    align-items: baseline;
    gap: 6px;
    padding: 2px 0;
    line-height: 1.5;
}
.about-zh {
    font-size: 10px;
    color: var(--text);
    flex-shrink: 0;
}
.about-en {
    font-size: 9px;
    color: var(--text-muted);
    opacity: 0.7;
}
.about-sub {
    padding-left: 12px;
}
.about-sub .about-en {
    font-style: italic;
    opacity: 0.5;
}

/* ═══ MAIN 3D AREA ════════════════════════════════════════════════════════ */
#main {
    flex: 1;
    position: relative;
    overflow: hidden;
}

#canvas {
    display: block;
    width: 100%;
    height: 100%;
}
#canvas.fps-mode { cursor: none; }

#topbar {
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    height: 36px;
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 0 16px;
    background: var(--overlay-bg);
    border-bottom: 1px solid var(--border);
    backdrop-filter: blur(8px);
    pointer-events: none;
    z-index: 10;
}
.topbar-left {
    font-size: 10px;
    letter-spacing: 2px;
    color: var(--text-muted);
}
.topbar-right {
    font-size: 9px;
    letter-spacing: 3px;
    color: var(--text-muted);
    opacity: 0.5;
}

/* FPS overlay */
#fps-overlay {
    display: none;
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    text-align: center;
    z-index: 20;
    pointer-events: none;
}
.click-hint {
    font-size: 18px;
    color: var(--accent-hover);
    margin-bottom: 12px;
    animation: pulse 2s infinite;
}
.key-hints {
    font-size: 11px;
    color: var(--text-muted);
}
.key-hints kbd {
    display: inline-block;
    padding: 2px 6px;
    background: var(--kbd-bg);
    border: 1px solid var(--border);
    border-radius: 3px;
    font-family: 'Space Mono', monospace;
    font-size: 10px;
    color: var(--text);
    margin: 0 1px;
}

@keyframes pulse {
    0%, 100% { opacity: 1; }
    50% { opacity: 0.5; }
}

/* Crosshair */
#crosshair {
    display: none;
    position: absolute;
    top: 50%;
    left: 50%;
    width: 20px;
    height: 20px;
    transform: translate(-50%, -50%);
    z-index: 15;
    pointer-events: none;
}
#crosshair::before,
#crosshair::after {
    content: '';
    position: absolute;
    background: rgba(255,255,255,0.5);
}
#crosshair::before {
    top: 50%;
    left: 0;
    right: 0;
    height: 1px;
    transform: translateY(-50%);
}
#crosshair::after {
    left: 50%;
    top: 0;
    bottom: 0;
    width: 1px;
    transform: translateX(-50%);
}

/* Loading */
#loading {
    display: none;
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: var(--overlay-heavy);
    z-index: 30;
    align-items: center;
    justify-content: center;
    flex-direction: column;
    gap: 16px;
    font-size: 11px;
    letter-spacing: 3px;
    color: var(--text-muted);
}

.spinner {
    width: 32px;
    height: 32px;
    border: 3px solid var(--border);
    border-top-color: var(--accent-hover);
    border-radius: 50%;
    animation: spin 0.8s linear infinite;
}

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

/* ═══ MOBILE ELEMENTS (hidden on desktop) ═══════════════════════════════ */
.drawer-handle {
    display: none;
    justify-content: center;
    padding: 8px 0 4px;
    cursor: grab;
}
.drawer-handle span {
    width: 36px;
    height: 4px;
    border-radius: 2px;
    background: var(--border);
}
#mobileBar {
    display: none;
}
.mobile-btn {
    width: 48px;
    height: 48px;
    border-radius: 12px;
    border: 1px solid var(--border);
    background: var(--panel-raised);
    color: var(--text);
    font-size: 20px;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: all 0.2s;
}
.mobile-btn:active {
    background: var(--accent);
    color: #fff;
    transform: scale(0.95);
}
/* Mobile overlay behind drawer */
#mobileOverlay {
    display: none;
    position: fixed;
    inset: 0;
    background: rgba(0,0,0,0.5);
    z-index: 45;
}

/* ═══ EMBED MODE ═══════════════════════════════════════════════════════ */
.embed-mode #panel,
.embed-mode #mobileBar,
.embed-mode .mode-hud,
.embed-mode .watermark { display: none !important; }
.embed-mode #main { width: 100vw !important; }
.embed-mode body { overflow: hidden; }

/* ═══ MOBILE RESPONSIVE ═════════════════════════════════════════════════ */
@media (max-width: 768px) {
    :root, [data-mode="dark"], [data-mode="light"] {
        --panel-padding: 16px;
        --btn-sm: 36px;
        --btn-xs: 30px;
        --input-size: 44px;
    }

    /* Layout: canvas fullscreen, panel as bottom drawer */
    body { flex-direction: column; }

    #main {
        width: 100%;
        height: 100dvh;
        flex: 1;
    }

    #panel {
        position: fixed;
        bottom: 0; left: 0; right: 0;
        width: 100% !important;
        min-width: 0 !important;
        max-height: 75dvh;
        border-right: none;
        border-top: 1px solid var(--border);
        border-radius: 16px 16px 0 0;
        transform: translateY(100%);
        transition: transform 0.3s cubic-bezier(0.4, 0, 0.2, 1);
        z-index: 50;
        overflow-y: auto;
    }
    #panel.open {
        transform: translateY(0);
    }

    /* Drawer handle visible on mobile */
    .drawer-handle { display: flex; }

    /* Mobile bar visible */
    #mobileBar {
        display: flex;
        position: fixed;
        bottom: 0; left: 0; right: 0;
        height: 64px;
        background: var(--panel);
        border-top: 1px solid var(--border);
        z-index: 40;
        align-items: center;
        justify-content: center;
        gap: 16px;
        padding: 0 24px;
    }

    /* Canvas needs bottom padding for mobile bar */
    #main { padding-bottom: 64px; }

    /* Compact panel header */
    .panel-header {
        padding: 10px var(--panel-padding) 8px;
    }
    .logo { font-size: 18px; letter-spacing: 4px; text-indent: 4px; }
    .tagline { font-size: 7px; letter-spacing: 2px; }

    /* Hide topbar on mobile (orbit instructions) */
    #topbar { display: none; }

    /* Hide FPS button on mobile */
    .seg-btn[data-mode="fps"] { display: none; }

    /* Draw canvas responsive */
    .draw-canvas {
        width: min(28vw, 140px);
        height: min(28vw, 140px);
    }

    /* Generate button (when inside panel) */
    .btn-gen {
        margin: 8px var(--panel-padding);
        width: calc(100% - var(--panel-padding) * 2);
    }

    /* Section content tighter */
    .section-content {
        padding: 0 var(--panel-padding) 12px;
    }
}