:root {
            --bg-base: #121316;
            --bg-panel: #1a1c22;
            --bg-card: #22252e;
            --bg-card-hover: #2a2e39;
            --border-color: #2e3340;
            --text-primary: #e6edf3;
            --text-secondary: #8b949e;
            --text-dim: #6e7681;
            --accent-cyan: #38bdf8;
            --accent-orange: #fb923c;
            --accent-green: #4ade80;
            --accent-yellow: #facc15;
            --accent-blue: #3b82f6;
            --accent-purple: #c084fc;
            --accent-red: #ef4444;
        }

        * {
            box-sizing: border-box;
            margin: 0;
            padding: 0;
            font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
            -webkit-font-smoothing: antialiased;
        }

        body {
            background-color: var(--bg-base);
            color: var(--text-primary);
            overflow: hidden;
            display: flex;
            height: 100vh;
            width: 100vw;
            user-select: none;
        }

        /* --- Sidebar Layout --- */
        #sidebar {
            width: 360px;
            min-width: 330px;
            max-width: 440px;
            background: var(--bg-panel);
            border-right: 1px solid var(--border-color);
            display: flex;
            flex-direction: column;
            height: 100%;
            z-index: 10;
            box-shadow: 4px 0 24px rgba(0, 0, 0, 0.4);
        }

        #sidebar-header {
            padding: 14px 18px;
            border-bottom: 1px solid var(--border-color);
            background: rgba(255, 255, 255, 0.02);
        }

        #sidebar-header h1 {
            font-size: 1.1rem;
            font-weight: 700;
            letter-spacing: -0.02em;
            color: #fff;
            display: flex;
            align-items: center;
            gap: 8px;
        }

        #sidebar-header p {
            font-size: 0.76rem;
            color: var(--text-secondary);
            margin-top: 3px;
            line-height: 1.3;
        }

        #sidebar-content {
            flex: 1;
            overflow-y: auto;
            padding: 14px 18px 40px 18px;
            display: flex;
            flex-direction: column;
            gap: 14px;
        }

        /* --- Collapsible Sections & Cards --- */
        .section-card {
            background: var(--bg-card);
            border: 1px solid var(--border-color);
            border-radius: 8px;
            padding: 12px 14px;
            display: flex;
            flex-direction: column;
            gap: 10px;
        }

        .section-title {
            font-size: 0.8rem;
            font-weight: 600;
            text-transform: uppercase;
            letter-spacing: 0.05em;
            color: var(--text-secondary);
            display: flex;
            align-items: center;
            justify-content: space-between;
        }

        /* --- Metrics Grid --- */
        .metrics-grid {
            display: grid;
            grid-template-columns: 1fr 1fr;
            gap: 6px;
        }

        .metric-item {
            background: rgba(0, 0, 0, 0.25);
            padding: 7px 9px;
            border-radius: 6px;
            border: 1px solid rgba(255, 255, 255, 0.04);
        }

        .metric-label {
            font-size: 0.7rem;
            color: var(--text-secondary);
            font-weight: 500;
        }

        .metric-value {
            font-size: 0.9rem;
            font-weight: 700;
            color: #fff;
            margin-top: 2px;
            font-variant-numeric: tabular-nums;
        }

        /* --- Control Rows & Inputs --- */
        .control-row {
            display: flex;
            align-items: center;
            justify-content: space-between;
            gap: 10px;
            font-size: 0.8rem;
        }

        .control-row label {
            color: var(--text-primary);
            flex: 1;
        }

        input[type="range"] {
            flex: 1.2;
            accent-color: var(--accent-cyan);
            height: 4px;
            background: var(--border-color);
            border-radius: 4px;
            outline: none;
        }

        input[type="number"], input[type="text"], select {
            background: rgba(0, 0, 0, 0.35);
            border: 1px solid var(--border-color);
            color: #fff;
            padding: 4px 7px;
            border-radius: 5px;
            font-size: 0.8rem;
            width: 70px;
            text-align: right;
            outline: none;
        }

        input[type="text"] {
            width: 100%;
            text-align: left;
        }

        select {
            width: 100%;
            text-align: left;
        }

        .badge-locked {
            font-size: 0.65rem;
            background: rgba(74, 222, 128, 0.15);
            color: var(--accent-green);
            padding: 2px 6px;
            border-radius: 4px;
            font-weight: 600;
        }

        /* --- Button Groups --- */
        .btn-group {
            display: grid;
            grid-template-columns: repeat(3, 1fr);
            gap: 5px;
        }

        .btn-group-2 {
            display: grid;
            grid-template-columns: 1fr 1fr;
            gap: 5px;
        }

        button {
            background: var(--bg-card-hover);
            border: 1px solid var(--border-color);
            color: var(--text-primary);
            padding: 6px 8px;
            border-radius: 5px;
            font-size: 0.76rem;
            font-weight: 600;
            cursor: pointer;
            transition: all 0.15s ease;
            text-align: center;
        }

        button:hover {
            background: #333846;
            color: #fff;
            border-color: #4b5366;
        }

        button:active {
            transform: scale(0.98);
        }

        button.primary {
            background: #0284c7;
            border-color: #38bdf8;
            color: #fff;
        }

        button.primary:hover {
            background: #0369a1;
        }

        button.active-tool {
            background: #7c3aed !important;
            border-color: #c084fc !important;
            color: #fff !important;
            box-shadow: 0 0 10px rgba(192, 132, 252, 0.4);
        }

        .btn-sm {
            padding: 4px 7px;
            font-size: 0.7rem;
        }

        /* --- Mode Switcher Tabs --- */
        .mode-tabs {
            display: flex;
            background: rgba(0, 0, 0, 0.4);
            border-radius: 6px;
            padding: 3px;
            gap: 4px;
            margin: 10px 18px 0 18px;
            border: 1px solid var(--border-color);
        }

        .mode-tab {
            flex: 1;
            background: transparent;
            border: none;
            padding: 7px 6px;
            font-size: 0.76rem;
            font-weight: 600;
            color: var(--text-secondary);
            border-radius: 4px;
            cursor: pointer;
            transition: all 0.15s ease;
            text-align: center;
        }

        .mode-tab:hover {
            color: #fff;
            background: rgba(255, 255, 255, 0.05);
        }

        .mode-tab.active {
            background: var(--accent-blue);
            color: #fff;
            box-shadow: 0 2px 8px rgba(59, 130, 246, 0.4);
        }

        /* --- Animation Curve Widget --- */
        .curve-widget-container {
            background: rgba(0, 0, 0, 0.3);
            border: 1px solid var(--border-color);
            border-radius: 6px;
            padding: 6px;
            display: flex;
            flex-direction: column;
            gap: 6px;
        }

        #curve-canvas {
            width: 100%;
            height: 100px;
            background: #0d0e12;
            border-radius: 4px;
            display: block;
            cursor: crosshair;
        }

        /* --- Point & Surface Lists --- */
        .point-item, .cs-item {
            display: flex;
            align-items: center;
            justify-content: space-between;
            background: rgba(0, 0, 0, 0.2);
            padding: 5px 7px;
            border-radius: 5px;
            font-size: 0.76rem;
            gap: 6px;
        }

        .cs-item {
            border-left: 3px solid var(--accent-purple);
        }

        button.del-btn {
            background: rgba(239, 68, 68, 0.15);
            color: #f87171;
            border: 1px solid rgba(239, 68, 68, 0.3);
            padding: 1px 5px;
            border-radius: 4px;
        }

        button.del-btn:hover {
            background: #ef4444;
            color: #fff;
        }

        /* --- Canvas Viewport --- */
        #canvas-container {
            flex: 1;
            position: relative;
            height: 100%;
            background: #15171c;
            overflow: hidden;
        }

        canvas#viewport {
            display: block;
            width: 100%;
            height: 100%;
            cursor: crosshair;
        }

        /* --- Floating Viewport HUD Controls --- */
        #viewport-hud {
            position: absolute;
            bottom: 20px;
            right: 20px;
            display: flex;
            gap: 6px;
            background: rgba(26, 28, 34, 0.85);
            backdrop-filter: blur(8px);
            padding: 5px;
            border-radius: 8px;
            border: 1px solid var(--border-color);
            z-index: 5;
        }

        #viewport-hud button {
            width: 30px;
            height: 30px;
            padding: 0;
            display: flex;
            align-items: center;
            justify-content: center;
            font-size: 0.95rem;
        }

        #legend {
            position: absolute;
            top: 20px;
            right: 20px;
            background: rgba(26, 28, 34, 0.85);
            backdrop-filter: blur(8px);
            padding: 8px 12px;
            border-radius: 8px;
            border: 1px solid var(--border-color);
            font-size: 0.72rem;
            display: flex;
            flex-direction: column;
            gap: 5px;
            z-index: 5;
            pointer-events: none;
        }

        .legend-item {
            display: flex;
            align-items: center;
            gap: 8px;
        }

        .legend-dot {
            width: 9px;
            height: 9px;
            border-radius: 50%;
        }

        .legend-line {
            width: 14px;
            height: 3px;
            border-radius: 2px;
        }

        /* --- Toast Banner --- */
        #toast {
            position: absolute;
            top: 20px;
            left: 50%;
            transform: translateX(-50%);
            background: rgba(239, 68, 68, 0.9);
            color: #fff;
            padding: 8px 16px;
            border-radius: 6px;
            font-size: 0.8rem;
            font-weight: 600;
            display: none;
            z-index: 50;
            box-shadow: 0 4px 16px rgba(0, 0, 0, 0.4);
            animation: fadeIn 0.2s ease;
        }

        @keyframes fadeIn {
            from { opacity: 0; transform: translate(-50%, -10px); }
            to { opacity: 1; transform: translate(-50%, 0); }
        }

        /* --- Context Menu --- */
        #context-menu {
            position: fixed;
            background: var(--bg-panel);
            border: 1px solid var(--border-color);
            border-radius: 6px;
            box-shadow: 0 8px 24px rgba(0, 0, 0, 0.6);
            display: none;
            flex-direction: column;
            min-width: 180px;
            padding: 4px;
            z-index: 1000;
        }

        .context-menu-item {
            padding: 7px 10px;
            font-size: 0.76rem;
            color: var(--text-primary);
            cursor: pointer;
            border-radius: 4px;
            display: flex;
            align-items: center;
            gap: 8px;
        }

        .context-menu-item:hover {
            background: var(--bg-card-hover);
            color: #fff;
        }

        .context-menu-divider {
            height: 1px;
            background: var(--border-color);
            margin: 4px 0;
        }