.supermarket-arena {
            height: 220px;
            background: linear-gradient(180deg, #fff3e0 0%, #ffcc80 100%);
            box-shadow: inset 0 0 15px rgba(0,0,0,0.1);
            position: relative;
            overflow: hidden;
            border: 5px solid #ff9800;
            border-radius: 12px;
        }

        /* Quầy thu ngân */
        .checkout-counter {
            position: absolute;
            bottom: -20px;
            left: 0;
            width: 100%;
            height: 80px;
            background: linear-gradient(90deg, #795548, #5d4037);
            border-top: 5px solid #3e2723;
            z-index: 2;
        }

        /* Máy tính tiền (POS) */
        .pos-machine {
            position: absolute;
            bottom: 40px;
            right: 10%;
            font-size: 5rem;
            z-index: 3;
            transition: all 0.3s ease;
        }

        /* Giỏ hàng của khách */
        .shopping-cart {
            position: absolute;
            bottom: 30px;
            left: 10%;
            font-size: 5rem;
            z-index: 3;
            animation: cart-bob 2s infinite alternate ease-in-out;
        }
        @keyframes cart-bob {
            0% { transform: translateY(0); }
            100% { transform: translateY(-5px); }
        }

        /* Hoạt ảnh thanh toán đúng (Ngăn kéo bật ra) */
        .checkout-success {
            animation: pos-ring 0.6s cubic-bezier(0.175, 0.885, 0.32, 1.275) forwards;
        }
        @keyframes pos-ring {
            0% { transform: scale(1); filter: drop-shadow(0 0 0px #4caf50); }
            50% { transform: scale(1.1); filter: drop-shadow(0 0 20px #4caf50); }
            100% { transform: scale(1); filter: drop-shadow(0 0 5px #4caf50); }
        }

        /* Hoạt ảnh thanh toán sai (Máy báo lỗi) */
        .checkout-error {
            animation: pos-error 0.4s infinite;
        }
        @keyframes pos-error {
            0% { transform: translateX(0); filter: drop-shadow(0 0 10px #f44336); }
            25% { transform: translateX(-5px); }
            50% { transform: translateX(5px); }
            75% { transform: translateX(-5px); }
            100% { transform: translateX(0); filter: drop-shadow(0 0 0px #f44336); }
        }

        /* CSS Vẽ Tờ Tiền (Dùng tạm khi chưa có ảnh thật) */
        .money-note {
            display: inline-block;
            padding: 5px 15px;
            margin: 5px;
            border-radius: 5px;
            border: 2px dashed rgba(255,255,255,0.7);
            font-weight: bold;
            color: white;
            box-shadow: 2px 2px 5px rgba(0,0,0,0.3);
            text-shadow: 1px 1px 2px rgba(0,0,0,0.8);
        }
        .note-10k { background-color: #d32f2f; } /* Đỏ */
        .note-20k { background-color: #1976d2; } /* Xanh dương */
        .note-50k { background-color: #c2185b; } /* Hồng đậm */
        .note-100k { background-color: #388e3c; } /* Xanh lá */

        .min-h-75 { min-height: 100px; }
        .hl-num { color: #e65100; font-weight: 900; font-size: 1.2em;