* {
            margin: 0;
            padding: 0;
            box-sizing: border-box;
            font-family: 'Segoe UI', 'Arial', system-ui, sans-serif;
        }
        body {
            background: #f2f7fd;
            color: #1a2b3c;
            padding: 20px;
        }
        .container {
            max-width: 1400px;
            margin: 0 auto;
            background: white;
            border-radius: 32px;
            box-shadow: 0 20px 60px rgba(0,20,40,0.06);
            padding: 24px 28px 40px;
        }
        /* Header */
        .config-header {
            text-align: center;
            padding: 30px 0 20px;
            border-bottom: 2px solid #eaf0f6;
            margin-bottom: 30px;
        }
        .config-header h1 {
            font-size: 2.6rem;
            font-weight: 700;
            background: linear-gradient(135deg, #0077be, #00b4d8);
            -webkit-background-clip: text;
            -webkit-text-fill-color: transparent;
            letter-spacing: -0.5px;
        }
        .config-subtitle {
            font-size: 1.1rem;
            color: #3a5e7a;
            margin-top: 8px;
        }
        /* Steps */
        .config-steps {
            display: flex;
            justify-content: center;
            flex-wrap: wrap;
            gap: 12px 28px;
            margin: 25px 0 10px;
        }
        .step {
            display: flex;
            align-items: center;
            gap: 8px;
            cursor: default;
            opacity: 0.6;
            transition: 0.2s;
        }
        .step.active {
            opacity: 1;
            font-weight: 600;
        }
        .step-circle {
            display: inline-flex;
            align-items: center;
            justify-content: center;
            width: 34px;
            height: 34px;
            border-radius: 50%;
            background: #e2ecf6;
            color: #1f4970;
            font-weight: 700;
            font-size: 0.9rem;
        }
        .step.active .step-circle {
            background: #0077be;
            color: white;
            box-shadow: 0 4px 10px rgba(0,119,190,0.25);
        }
        .step-label {
            font-size: 0.95rem;
            color: #1f3b54;
        }
        .step.active .step-label {
            color: #0077be;
        }

        /* Sections */
        .config-section {
            display: none;
            animation: fadeIn 0.35s ease;
        }
        .config-section.active {
            display: block;
        }
        @keyframes fadeIn {
            0% { opacity: 0.4; transform: translateY(6px); }
            100% { opacity: 1; transform: translateY(0); }
        }

        .section-header {
            display: flex;
            align-items: center;
            gap: 16px;
            margin-bottom: 28px;
            padding-bottom: 12px;
            border-bottom: 2px solid #ecf3fa;
        }
        .section-icon {
            width: 52px;
            height: 52px;
            background: #e7f0fa;
            border-radius: 14px;
            display: flex;
            align-items: center;
            justify-content: center;
            color: #0077be;
            font-size: 1.8rem;
        }
        .section-title {
            font-size: 1.7rem;
            font-weight: 700;
            color: #0a1e30;
        }
        .section-subtitle {
            color: #4f6f8a;
            font-size: 0.95rem;
        }

        /* Cards */
        .options-grid {
            display: grid;
            grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
            gap: 22px;
            margin-bottom: 10px;
        }
        .option-card {
            background: white;
            border: 2px solid #e2ebf3;
            border-radius: 18px;
            padding: 20px 18px 18px;
            transition: all 0.2s;
            cursor: pointer;
            position: relative;
        }
        .option-card:hover {
            border-color: #7bb3d9;
            transform: translateY(-3px);
            box-shadow: 0 8px 18px rgba(0,80,130,0.06);
        }
        .option-card.selected {
            border-color: #0077be;
            background: #f7fcff;
            box-shadow: 0 6px 14px rgba(0,119,190,0.08);
        }
        .option-card.selected::after {
            content: "✓";
            position: absolute;
            top: 12px;
            right: 16px;
            font-size: 1.2rem;
            font-weight: 700;
            color: #0077be;
        }
        .option-header {
            display: flex;
            align-items: center;
            gap: 14px;
            margin-bottom: 12px;
        }
        .option-icon {
            width: 44px;
            height: 44px;
            background: #eef6fe;
            border-radius: 12px;
            display: flex;
            align-items: center;
            justify-content: center;
            color: #0077be;
            font-size: 1.4rem;
        }
        .option-title {
            font-size: 1.2rem;
            font-weight: 700;
            color: #0a1e30;
        }
        .option-desc {
            color: #2f5270;
            font-size: 0.92rem;
            margin: 6px 0 12px;
        }
        .option-specs {
            margin-top: 10px;
            border-top: 1px solid #e8eff6;
            padding-top: 12px;
        }
        .spec-item {
            display: flex;
            justify-content: space-between;
            font-size: 0.85rem;
            padding: 3px 0;
            color: #1f3b54;
        }
        .spec-value {
            font-weight: 600;
            color: #0077be;
        }

        /* N‑Series direct selection grid */
        .n-board-grid {
            display: grid;
            grid-template-columns: repeat(auto-fill, minmax(200px, 1fr));
            gap: 14px;
            margin: 18px 0 20px;
        }
        .n-board-card {
            background: #fafdff;
            border: 2px solid #e2ebf3;
            border-radius: 16px;
            padding: 16px 14px;
            cursor: pointer;
            transition: all 0.15s;
            text-align: center;
            display: flex;
            flex-direction: column;
            align-items: center;
            gap: 4px;
        }
        .n-board-card:hover {
            border-color: #90bada;
            background: #f5faff;
        }
        .n-board-card.selected {
            border-color: #0077be;
            background: #e8f3fd;
            box-shadow: 0 4px 12px rgba(0,119,190,0.10);
        }
        .n-board-card .model-badge {
            font-weight: 700;
            font-size: 1.1rem;
            color: #0a1e30;
        }
        .n-board-card .model-desc {
            font-size: 0.8rem;
            color: #3a5e7a;
            line-height: 1.4;
        }
        .n-board-card .ch-badge {
            background: #dce8f5;
            padding: 0 12px;
            border-radius: 20px;
            font-size: 0.7rem;
            font-weight: 600;
            color: #1f4970;
            margin-top: 6px;
        }
        .n-board-card .qty-indicator {
            font-size: 0.75rem;
            color: #0077be;
            font-weight: 600;
            margin-top: 4px;
            background: #e7f0fa;
            padding: 2px 12px;
            border-radius: 30px;
        }

        /* Selected list */
        .selected-n-list {
            background: #f4f9ff;
            border-radius: 18px;
            padding: 18px 22px;
            margin: 20px 0 10px;
            border: 1px solid #d7e5f2;
            display: flex;
            flex-wrap: wrap;
            align-items: center;
            gap: 8px 14px;
        }
        .selected-n-list .label {
            font-weight: 600;
            color: #0a1e30;
            margin-right: 8px;
        }
        .selected-n-item {
            display: inline-flex;
            align-items: center;
            gap: 8px;
            background: white;
            border-radius: 40px;
            padding: 4px 14px 4px 16px;
            border: 1px solid #c4d8ea;
            box-shadow: 0 2px 4px rgba(0,0,0,0.02);
            font-size: 0.9rem;
        }
        .selected-n-item .remove-n {
            background: none;
            border: none;
            color: #a0b8cf;
            cursor: pointer;
            font-size: 1rem;
            padding: 0 2px;
        }
        .selected-n-item .remove-n:hover {
            color: #c0392b;
        }
        .n-empty {
            color: #6f8ba8;
            font-size: 0.95rem;
        }
        .power-warning {
            background: #fff3e0;
            border-left: 4px solid #f39c12;
            padding: 10px 18px;
            border-radius: 12px;
            margin: 12px 0 6px;
            color: #7f6000;
            font-weight: 500;
            display: flex;
            align-items: center;
            gap: 12px;
            flex-wrap: wrap;
        }
        .power-warning .btn-add-power {
            background: #0077be;
            color: white;
            border: none;
            padding: 6px 20px;
            border-radius: 40px;
            font-weight: 600;
            cursor: pointer;
            font-size: 0.85rem;
        }
        .power-warning .btn-add-power:hover {
            background: #005f9e;
        }

        /* Nav */
        .config-nav {
            display: flex;
            justify-content: space-between;
            margin-top: 38px;
            padding-top: 24px;
            border-top: 1px solid #e2ebf3;
            flex-wrap: wrap;
            gap: 12px;
        }
        .nav-btn {
            background: #eef4fa;
            border: none;
            padding: 10px 30px;
            border-radius: 60px;
            font-weight: 600;
            font-size: 0.95rem;
            color: #1f4970;
            cursor: pointer;
            transition: 0.15s;
            display: inline-flex;
            align-items: center;
            gap: 8px;
        }
        .nav-btn:hover:not(:disabled) {
            background: #d5e3f0;
        }
        .nav-btn.primary {
            background: #0077be;
            color: white;
            box-shadow: 0 4px 10px rgba(0,119,190,0.15);
        }
        .nav-btn.primary:hover {
            background: #005f9e;
            transform: scale(1.02);
        }
        .nav-btn:disabled {
            opacity: 0.45;
            cursor: not-allowed;
        }

        /* Result */
        .result-section {
            display: none;
            margin-top: 30px;
            background: #f9fcff;
            border-radius: 28px;
            padding: 30px 32px;
            border: 1px solid #dae6f2;
        }
        .result-section.active {
            display: block;
            animation: fadeIn 0.4s;
        }
        .final-model {
            background: #e3effa;
            border-radius: 20px;
            padding: 20px;
            text-align: center;
            font-size: 2rem;
            font-weight: 700;
            color: #004b7a;
            word-break: break-all;
        }
        .specs-summary {
            display: grid;
            grid-template-columns: repeat(auto-fill, minmax(220px,1fr));
            gap: 18px;
            margin: 24px 0 10px;
        }
        .spec-summary-card {
            background: white;
            border-radius: 16px;
            padding: 16px 18px;
            border: 1px solid #e2ebf3;
        }
        .spec-summary-title {
            font-weight: 700;
            color: #0077be;
            margin-bottom: 6px;
            font-size: 0.9rem;
            text-transform: uppercase;
            letter-spacing: 0.3px;
        }

        /* Wireless & software */
        .wireless-options {
            display: flex;
            flex-wrap: wrap;
            gap: 14px;
            margin: 12px 0 18px;
        }
        .wireless-option {
            background: white;
            border: 2px solid #e2ebf3;
            border-radius: 16px;
            padding: 12px 20px;
            cursor: pointer;
            text-align: center;
            flex: 1 0 100px;
            transition: 0.15s;
        }
        .wireless-option:hover {
            border-color: #7bb3d9;
        }
        .wireless-option.selected {
            border-color: #0077be;
            background: #f0f8ff;
        }
        .wireless-icon {
            font-size: 1.6rem;
            color: #3a5e7a;
        }
        .wireless-title {
            font-weight: 600;
            color: #0a1e30;
        }
        .wireless-desc {
            font-size: 0.75rem;
            color: #4f6f8a;
        }

        @media (max-width: 640px) {
            .container { padding: 16px; }
            .config-header h1 { font-size: 1.8rem; }
            .options-grid { grid-template-columns: 1fr; }
            .n-board-grid { grid-template-columns: repeat(auto-fill, minmax(150px,1fr)); }
        }