.zener-app-container {
            --bg-primary: #0f172a;
            --card-bg: #1e293b;
            --accent-blue: #38bdf8;
            --accent-green: #22c55e;
            --accent-red: #ef4444;
            --text-main: #f8fafc;
            --text-muted: #FFFFFF;
            --card-back: #334155;

            width: 100%;
            max-width: 100%;
            box-sizing: border-box;
            background-color: var(--bg-primary);
            color: var(--text-main);
            padding: clamp(0.75rem, 3vw, 1.5rem);
            border-radius: 16px;
            display: flex;
            flex-direction: column;
            align-items: center;
            font-family: 'Segoe UI', system-ui, -apple-system, sans-serif;
            user-select: none;
            container-type: inline-size; 
        }

        .zener-app-container * {
            box-sizing: border-box;
            margin: 0;
            padding: 0;
        }

        .zener-app-container header {
            text-align: center;
            margin-bottom: 1rem;
            width: 100%;
        }

        .zener-app-container h1 {
            font-size: clamp(1.2rem, 4cqi, 1.8rem);
            color: var(--accent-blue);
            margin-bottom: 0.2rem;
            line-height: 1.2;
        }

        .zener-app-container p.subtitle {
            font-size: clamp(0.75rem, 2.5cqi, 0.9rem);
            color: var(--text-muted);
        }

        .zener-app-container .dashboard {
            display: grid;
            grid-template-columns: repeat(3, 1fr);
            gap: 0.5rem;
            width: 100%;
            max-width: 600px;
            background: var(--card-bg);
            padding: 0.75rem;
            border-radius: 12px;
            box-shadow: 0 4px 20px rgba(0,0,0,0.3);
            margin-bottom: 1rem;
        }

        .zener-app-container .stat-box {
             font-weight: bold;
            text-align: center;
        }

        .zener-app-container .stat-label {
            font-size: clamp(0.65rem, 2cqi, 0.75rem);
            text-transform: uppercase;
            color: var(--text-muted);
            margin-bottom: 0.2rem;
        }

        .zener-app-container .stat-value {
            font-size: clamp(1rem, 3.5cqi, 1.4rem);
            font-weight: bold;
        }

        .zener-app-container .main-stage {
            display: flex;
            flex-direction: column;
            align-items: center;
            justify-content: center;
            width: 100%;
            max-width: 600px;
        }

        .zener-app-container .card-container {
            perspective: 1000px;
            width: clamp(90px, 25cqi, 140px);
            aspect-ratio: 0.7;
            margin-bottom: 1.2rem;
        }

        .zener-app-container .card {
            width: 100%;
            height: 100%;
            position: relative;
            transform-style: preserve-3d;
            transition: transform 0.6s cubic-bezier(0.4, 0, 0.2, 1);
            border-radius: 12px;
            box-shadow: 0 8px 25px rgba(0,0,0,0.5);
        }

        .zener-app-container .card.flipped {
            transform: rotateY(180deg);
        }

        .zener-app-container .card-face {
            position: absolute;
            width: 100%;
            height: 100%;
            backface-visibility: hidden;
            border-radius: 12px;
            display: flex;
            align-items: center;
            justify-content: center;
            border: 2px solid #475569;
        }

        .zener-app-container .card-front {
            background-color: var(--card-back);
            background-image: radial-gradient(#475569 1px, transparent 1px);
            background-size: 10px 10px;
        }

        .zener-app-container .card-back {
            background-color: #ffffff;
            transform: rotateY(180deg);
        }

        .zener-app-container .symbol-svg {
            width: 55%;
            height: 55%;
            stroke: #0f172a;
            stroke-width: 8;
            fill: none;
            stroke-linecap: round;
            stroke-linejoin: round;
        }

        .zener-app-container .controls {
            display: flex;
            gap: clamp(0.3rem, 1.5cqi, 0.8rem);
            justify-content: center;
            flex-wrap: wrap;
            width: 100%;
            margin-bottom: 1rem;
        }

        .zener-app-container .symbol-btn {
            background: var(--card-bg);
            border: 2px solid #475569;
            border-radius: 10px;
            width: clamp(44px, 12cqi, 60px);
            height: clamp(44px, 12cqi, 60px);
            cursor: pointer;
            display: flex;
            align-items: center;
            justify-content: center;
            transition: all 0.2s ease;
            flex-shrink: 0;
        }

        .zener-app-container .symbol-btn .symbol-svg {
            width: 60%;
            height: 60%;
            stroke: var(--text-main);
            stroke-width: 6;
        }

        .zener-app-container .symbol-btn:hover:not(:disabled) {
            border-color: var(--accent-blue);
            transform: translateY(-2px);
            background: #334155;
        }

        .zener-app-container .symbol-btn:active:not(:disabled) {
            transform: translateY(0);
        }

        .zener-app-container .symbol-btn:disabled {
            opacity: 0.4;
            cursor: not-allowed;
        }

        .zener-app-container .message-area {
            min-height: 2.2rem;
            font-size: clamp(0.8rem, 2.5cqi, 1rem);
            font-weight: 600;
            text-align: center;
            margin-bottom: 0.8rem;
            display: flex;
            align-items: center;
            justify-content: center;
        }

        .zener-app-container .msg-correct { color: var(--accent-green); }
        .zener-app-container .msg-wrong { color: var(--accent-red); }

        .zener-app-container .action-btn {
            background: var(--accent-blue);
            color: var(--bg-primary);
            border: none;
            padding: 0.6rem 1.2rem;
            font-size: clamp(0.85rem, 2.5cqi, 1rem);
            font-weight: bold;
            border-radius: 8px;
            cursor: pointer;
            transition: opacity 0.2s;
            margin-bottom: 1rem;
        }

        .zener-app-container .action-btn:hover {
            opacity: 0.9;
        }

        .zener-app-container .history-panel {
            width: 100%;
            max-width: 600px;
            background: var(--card-bg);
            border-radius: 12px;
            padding: 0.8rem;
            font-size: clamp(0.75rem, 2.2cqi, 0.85rem);
        }

        .zener-app-container .history-title {
            color: var(--text-muted);
            margin-bottom: 0.4rem;
            text-transform: uppercase;
            font-size: clamp(0.65rem, 2cqi, 0.75rem);
            text-align: center;
        }

        .zener-app-container .history-stats {
            display: flex;
            justify-content: space-around;
            flex-wrap: wrap;
            gap: 0.5rem;
            color: var(--text-main);
        }