:root {
            --bg-color: #041b23;
            --container-bg: #06262f;
            --panel-bg: #0a323d;
            --border-color: #124a58;
            --panel-sunken: rgba(0, 0, 0, 0.3);
            --text-primary: #d9f2f5;
            --text-secondary: #6f9aa5;
            --accent-teal: #22d3ee;
            --accent-amber: #fbbf24;
            --accent-red: #f04b5c;
            --accent-green: #34d399;
            --display-font: 'Chakra Petch', sans-serif;
            --mono-font: 'Exo 2', sans-serif;
            --shadow-color: rgba(0, 0, 0, 0.6);

            /* Shared kit mapping */
            --kit-accent: var(--accent-teal);
            --kit-accent-ink: #022026;
            --kit-accent-glow: rgba(34, 211, 238, 0.25);
            --kit-surface: var(--panel-bg);
            --kit-border: var(--border-color);
            --kit-input-bg: var(--container-bg);
            --kit-error: var(--accent-red);

            /* Trench scope canvas (dark) — always themed, never hardcoded in JS */
            --canvas-bg-top: #08303c;
            --canvas-bg-bottom: #011016;
            --canvas-surface-line: rgba(217, 242, 245, 0.4);
            --canvas-rock: #103f47;
            --canvas-rock-edge: #1c5c66;
            --canvas-mine: #f04b5c;
            --canvas-mine-core: #ffe1a8;
            --canvas-sub-body: #fbbf24;
            --canvas-sub-window: #22d3ee;
            --canvas-safe-glow: rgba(52, 211, 153, 0.30);
            --canvas-safe-line: #34d399;
        }

        body.light-mode {
            --bg-color: #edf9fb;
            --container-bg: #ffffff;
            --panel-bg: #e1f3f7;
            --border-color: #bce2ea;
            --panel-sunken: rgba(0, 0, 0, 0.045);
            --text-primary: #0a2530;
            --text-secondary: #4d7480;
            --accent-teal: #0891b2;
            --accent-amber: #b45309;
            --accent-red: #b91c1c;
            --accent-green: #15803d;
            --shadow-color: rgba(10, 37, 48, 0.1);

            /* Shared kit mapping (light theme) */
            --kit-accent: var(--accent-teal);
            --kit-accent-ink: #f0fbfd;
            --kit-accent-glow: rgba(8, 145, 178, 0.15);
            --kit-surface: var(--panel-bg);
            --kit-border: var(--border-color);
            --kit-input-bg: var(--container-bg);
            --kit-error: var(--accent-red);

            /* Trench scope canvas (light) — re-declared explicitly, never inherited from dark */
            --canvas-bg-top: #cdeef5;
            --canvas-bg-bottom: #eaf8fb;
            --canvas-surface-line: rgba(10, 37, 48, 0.35);
            --canvas-rock: #8bb9c4;
            --canvas-rock-edge: #5f96a3;
            --canvas-mine: #b91c1c;
            --canvas-mine-core: #fde68a;
            --canvas-sub-body: #b45309;
            --canvas-sub-window: #0891b2;
            --canvas-safe-glow: rgba(21, 128, 61, 0.22);
            --canvas-safe-line: #15803d;
        }

        * {
            box-sizing: border-box;
            margin: 0;
            padding: 0;
            transition: background-color 0.25s ease, color 0.25s ease, border-color 0.25s ease;
        }

        body {
            background-color: var(--bg-color);
            color: var(--text-primary);
            font-family: var(--mono-font);
            min-height: 100vh;
            display: flex;
            flex-direction: column;
            align-items: center;
            justify-content: center;
            padding: 20px;
        }

        .top-controls {
            position: fixed;
            top: 20px;
            right: 24px;
            z-index: 1000;
        }

        .theme-toggle-btn {
            background: var(--container-bg);
            color: var(--text-primary);
            border: 2px solid var(--border-color);
            padding: 8px 16px;
            border-radius: 20px;
            font-family: var(--display-font);
            font-weight: 600;
            font-size: 0.85rem;
            cursor: pointer;
            box-shadow: 0 4px 10px var(--shadow-color);
        }

        .theme-toggle-btn:hover {
            border-color: var(--accent-teal);
        }

        .sonar-container {
            width: 100%;
            max-width: 860px;
            background: var(--container-bg);
            border: 2px solid var(--border-color);
            border-top: 6px solid var(--accent-teal);
            border-radius: 16px;
            padding: 32px;
            box-shadow: 0 12px 30px var(--shadow-color);
            min-height: 600px;
            display: flex;
            flex-direction: column;
            justify-content: space-between;
        }

        .hero-icon {
            font-size: 3rem;
            margin-bottom: 8px;
        }

        .sonar-title {
            font-family: var(--display-font);
            font-size: 1.7rem;
            font-weight: 700;
            color: var(--accent-teal);
            text-align: center;
            letter-spacing: 0.5px;
            margin-bottom: 8px;
        }

        .sonar-subtitle {
            font-family: var(--mono-font);
            text-align: center;
            color: var(--text-secondary);
            font-size: 0.95rem;
            margin-bottom: 20px;
            letter-spacing: 0.5px;
        }

        .screen-center {
            display: flex;
            flex-direction: column;
            align-items: center;
            justify-content: center;
            text-align: center;
            padding: 10px 0;
        }

        .brief-box {
            background: var(--panel-bg);
            border: 1px solid var(--border-color);
            border-radius: 12px;
            padding: 20px 28px;
            text-align: left;
            margin: 16px 0;
            max-width: 680px;
            line-height: 1.7;
            font-size: 0.93rem;
        }

        .brief-box ul { padding-left: 20px; }
        .brief-box li { margin-bottom: 8px; }

        .action-btn {
            background: var(--accent-teal);
            color: #022026;
            border: none;
            padding: 14px 36px;
            font-family: var(--display-font);
            font-size: 1rem;
            font-weight: 700;
            text-transform: uppercase;
            letter-spacing: 1px;
            cursor: pointer;
            margin-top: 18px;
            border-radius: 24px;
            box-shadow: 0 4px 12px var(--shadow-color);
        }

        .action-btn:hover { opacity: 0.92; }

        /* HUD Bar */
        .hud-bar {
            display: flex;
            justify-content: space-between;
            align-items: center;
            background: var(--panel-bg);
            border: 1px solid var(--border-color);
            padding: 12px 20px;
            margin-bottom: 18px;
            border-radius: 12px;
            gap: 12px;
            flex-wrap: wrap;
        }

        .hud-item {
            display: flex;
            flex-direction: column;
        }

        .hud-label {
            font-size: 0.72rem;
            color: var(--text-secondary);
            text-transform: uppercase;
            letter-spacing: 0.5px;
        }

        .hud-value {
            font-family: var(--display-font);
            font-weight: 700;
            font-size: 1rem;
            color: var(--accent-teal);
        }

        .hull-container {
            width: 160px;
            height: 12px;
            background: var(--border-color);
            border-radius: 6px;
            overflow: hidden;
            margin-top: 4px;
        }

        .hull-fill {
            height: 100%;
            width: 100%;
            background: var(--accent-green);
            transition: width 0.3s ease, background-color 0.3s ease;
        }

        /* Order Card */
        .order-card {
            background: var(--panel-bg);
            border: 1px solid var(--border-color);
            border-left: 4px solid var(--accent-teal);
            border-radius: 12px;
            padding: 18px 22px;
            margin-bottom: 18px;
        }

        .order-tag {
            font-family: var(--display-font);
            font-size: 0.7rem;
            text-transform: uppercase;
            color: var(--accent-teal);
            margin-bottom: 8px;
            letter-spacing: 1px;
        }

        .order-text {
            font-size: 1.08rem;
            line-height: 1.55;
            font-weight: 600;
        }

        /* Interaction Panel */
        .interaction-panel {
            background: var(--panel-bg);
            border: 1px solid var(--border-color);
            border-radius: 12px;
            padding: 20px 22px;
        }

        /* Steering Panel (trench scope + throttle controls) */
        .steering-panel {
            display: flex;
            gap: 18px;
            align-items: stretch;
            flex-wrap: wrap;
        }

        .scope-wrap {
            position: relative;
            flex: 1 1 320px;
            min-width: 240px;
        }

        #trenchCanvas {
            display: block;
            width: 100%;
            height: auto;
            aspect-ratio: 2 / 1;
            border-radius: 12px;
            border: 1px solid var(--border-color);
            background: var(--canvas-bg-bottom);
        }

        .scope-readout {
            position: absolute;
            top: 10px;
            right: 10px;
            padding: 8px 14px;
            min-width: 0;
            background: var(--panel-sunken);
            border: 1px solid var(--border-color);
            border-radius: 10px;
        }

        .throttle-controls {
            flex: 0 0 140px;
            display: flex;
            flex-direction: column;
            gap: 10px;
            align-items: stretch;
            justify-content: center;
        }

        .throttle-btn {
            background: var(--accent-teal);
            color: #022026;
            border: none;
            padding: 16px 8px;
            font-family: var(--display-font);
            font-size: 0.95rem;
            font-weight: 700;
            line-height: 1.3;
            letter-spacing: 0.5px;
            border-radius: 14px;
            cursor: pointer;
            box-shadow: 0 4px 12px var(--shadow-color);
            user-select: none;
            touch-action: none;
        }

        .throttle-btn.active,
        .throttle-btn:active {
            transform: scale(0.96);
            filter: brightness(1.08);
        }

        .throttle-hint {
            text-align: center;
            font-size: 0.72rem;
            color: var(--text-secondary);
            line-height: 1.3;
        }

        .depth-readout-box {
            display: flex;
            flex-direction: column;
            align-items: center;
            justify-content: center;
            background: var(--panel-sunken);
            border: 1px solid var(--border-color);
            border-radius: 10px;
            padding: 16px 20px;
            min-width: 120px;
        }

        .depth-readout-label {
            font-size: 0.72rem;
            color: var(--text-secondary);
            text-transform: uppercase;
            margin-bottom: 6px;
        }

        .depth-readout-value {
            font-family: var(--display-font);
            font-size: 1.8rem;
            font-weight: 700;
            color: var(--accent-amber);
        }

        .feedback-line {
            font-family: var(--mono-font);
            text-align: center;
            font-size: 0.98rem;
            font-weight: 700;
            min-height: 24px;
            margin-top: 14px;
        }

        .text-success { color: var(--accent-green); }
        .text-error { color: var(--accent-red); }

        .score-readout {
            font-family: var(--display-font);
            font-size: 1.15rem;
            background: var(--panel-bg);
            padding: 10px 22px;
            border: 1px solid var(--border-color);
            border-radius: 12px;
            margin-bottom: 12px;
            color: var(--accent-teal);
        }

        footer {
            margin-top: 20px;
            font-family: var(--mono-font);
            font-size: 0.8rem;
            color: var(--text-secondary);
            text-align: center;
        }

        @media (max-width: 640px) {
            .hud-bar { flex-direction: column; align-items: flex-start; }
            .steering-panel { flex-direction: column; }
            .throttle-controls { flex-direction: row; }
            .throttle-btn { flex: 1; }
            .throttle-hint { flex: 1; display: flex; align-items: center; justify-content: center; }
        }