:root {
            --primary-color: #2c353e;
            --primary-hover: #0044cc;
            --bg-color: #f5f5f7;
            --card-bg: #ffffff;
            --text-primary: #1a1a1a;
            --text-secondary: #6e6e73;
            --border-color: #d2d2d7;
            --success-color: #34c759;
            --danger-color: #ff3b30;
            --radius: 16px;
            --shadow: 0 4px 24px rgba(0, 0, 0, 0.06);
        }

        .container-calc {
            max-width: 700px;
            margin: 0 auto;
        }

        .calculator-card, .info-section, .history-card {
            background: var(--card-bg);
            border-radius: var(--radius);
            box-shadow: var(--shadow);
            padding: 24px;
            margin-bottom: 24px;
        }

        /* Tabs */
        .tabs {
            display: flex;
            background: #f0f0f2;
            border-radius: 12px;
            padding: 4px;
            margin-bottom: 24px;
        }

        .tab-btn {
            flex: 1;
            padding: 12px;
            border: none;
            background: transparent;
            color: var(--text-secondary);
            font-size: 16px;
            font-weight: 600;
            cursor: pointer;
            border-radius: 10px;
            transition: all 0.2s ease;
        }

        .tab-btn.active {
            background: var(--card-bg);
            color: var(--text-primary);
            box-shadow: 0 2px 8px rgba(0, 0, 0, 0.08);
        }

        /* Input Groups */
        .input-group {
            margin-bottom: 24px;
        }

        .input-group label {
            display: block;
            font-size: 14px;
            font-weight: 600;
            color: var(--text-secondary);
            margin-bottom: 8px;
        }

        .amount-input {
            width: 100%;
            padding: 16px;
            font-size: 24px;
            font-weight: 600;
            border: 2px solid var(--border-color);
            border-radius: 12px;
            outline: none;
            transition: border-color 0.2s;
            font-family: inherit;
        }

        .amount-input:focus {
            border-color: var(--primary-color);
        }

        .amount-input::placeholder {
            color: #c7c7cc;
        }

        /* Rates */
        .rates {
            display: flex;
            flex-wrap: wrap;
            gap: 8px;
        }

        .rate-option {
            position: relative;
        }

        .rate-option input {
            position: absolute;
            opacity: 0;
            cursor: pointer;
        }

        .rate-option span {
            display: block;
            padding: 10px 16px;
            background: #f0f0f2;
            border-radius: 8px;
            font-size: 15px;
            font-weight: 600;
            cursor: pointer;
            transition: all 0.2s;
            border: 2px solid transparent;
        }

        .rate-option input:checked + span {
            background: rgba(0, 85, 255, 0.08);
            border-color: var(--primary-color);
            color: var(--primary-color);
        }

        .rate-option:hover span {
            background: #e5e5ea;
        }

        .rate-note {
            font-size: 13px;
            color: var(--text-secondary);
            margin-top: 8px;
            line-height: 1.4;
        }

        /* Results */
        .results {
            border-top: 1px solid var(--border-color);
            padding-top: 24px;
            margin-top: 24px;
        }

        .results h3 {
            font-size: 18px;
            margin-bottom: 16px;
            font-weight: 600;
        }

        .result-item {
            display: flex;
            justify-content: space-between;
            align-items: center;
            padding: 16px 0;
            border-bottom: 1px solid #f0f0f2;
        }

        .result-item:last-of-type {
            border-bottom: none;
        }

        .result-label {
            font-size: 15px;
            color: var(--text-secondary);
            font-weight: 500;
        }

        .result-value {
            display: flex;
            align-items: center;
            gap: 12px;
        }

        .result-value span {
            font-size: 20px;
            font-weight: 700;
            color: var(--text-primary);
            min-width: 120px;
            text-align: right;
        }

        .copy-btn {
            background: #f0f0f2;
            border: none;
            color: var(--text-secondary);
            font-size: 13px;
            font-weight: 600;
            padding: 6px 12px;
            border-radius: 6px;
            cursor: pointer;
            transition: all 0.2s;
            white-space: nowrap;
        }

        .copy-btn:hover {
            background: #e5e5ea;
            color: var(--text-primary);
        }

        .copy-btn.copied {
            background: rgba(52, 199, 89, 0.15);
            color: var(--success-color);
        }

        /* Action Buttons */
        .actions {
            display: flex;
            gap: 12px;
            margin-top: 24px;
        }

        .btn-primary, .btn-secondary {
            flex: 1;
            padding: 14px;
            border-radius: 12px;
            font-size: 16px;
            font-weight: 600;
            cursor: pointer;
            transition: all 0.2s;
            border: none;
            text-align: center;
        }

        .btn-primary {
            background: var(--primary-color);
            color: white;
        }

        .btn-primary:hover {
            background: var(--primary-hover);
        }

        .btn-secondary {
            background: transparent;
            border: 1px solid var(--border-color);
            color: var(--text-secondary);
        }

        .btn-secondary:hover {
            background: #f0f0f2;
            color: var(--text-primary);
        }

        /* History Section */
        .history-header {
            display: flex;
            justify-content: space-between;
            align-items: center;
            margin-bottom: 16px;
        }

        .history-header h2 {
            font-size: 20px;
            font-weight: 700;
        }

        .clear-history-btn {
            background: transparent;
            border: none;
            color: var(--danger-color);
            font-size: 14px;
            font-weight: 600;
            cursor: pointer;
            padding: 4px 8px;
            border-radius: 6px;
        }

        .clear-history-btn:hover {
            background: rgba(255, 59, 48, 0.1);
        }

        .saved-item {
            background: #f9f9fa;
            border-radius: 12px;
            padding: 16px;
            margin-bottom: 12px;
            border: 1px solid #e5e5ea;
            transition: transform 0.2s;
        }

        .saved-item:hover {
            transform: translateY(-2px);
            box-shadow: 0 4px 12px rgba(0,0,0,0.04);
        }

        .saved-item-header {
            display: flex;
            justify-content: space-between;
            align-items: center;
            margin-bottom: 8px;
        }

        .saved-item-date {
            font-size: 13px;
            color: var(--text-secondary);
        }

        .delete-btn {
            background: transparent;
            border: none;
            color: var(--text-secondary);
            font-size: 13px;
            cursor: pointer;
            padding: 4px 8px;
            border-radius: 6px;
        }

        .delete-btn:hover {
            background: rgba(255, 59, 48, 0.1);
            color: var(--danger-color);
        }

        .saved-item-body strong {
            font-size: 15px;
            color: var(--text-primary);
        }

        .saved-item-details {
            display: flex;
            gap: 16px;
            margin-top: 8px;
            font-size: 14px;
            color: var(--text-secondary);
        }

        .saved-item-details strong {
            color: var(--text-primary);
        }

        .empty-history {
            text-align: center;
            color: var(--text-secondary);
            padding: 24px;
            font-size: 15px;
        }

        /* Formula Block */
        .formula-block {
            margin-bottom: 20px;
            padding: 16px;
            background: #f9f9fa;
            border-radius: 12px;
        }

        .formula-block h3 {
            font-size: 16px;
            margin-bottom: 8px;
            color: var(--text-primary);
        }

        .formula-block p {
            font-size: 14px;
            color: var(--text-secondary);
            margin-bottom: 4px;
            font-family: "SF Mono", Monaco, monospace;
            background: #fff;
            padding: 8px 12px;
            border-radius: 6px;
            border: 1px solid #e5e5ea;
        }

        @media (max-width: 480px) {
            .result-value {
                flex-direction: column;
                align-items: flex-end;
                gap: 8px;
            }
            .result-value span {
                font-size: 18px;
            }
            .rates {
                gap: 6px;
            }
            .rate-option span {
                padding: 8px 12px;
                font-size: 14px;
            }
            .actions {
                flex-direction: column;
            }
        }