* {
            margin: 0;
            padding: 0;
            box-sizing: border-box;
        }

        body {
            font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
            background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
            min-height: 100vh;
            display: flex;
            justify-content: center;
            align-items: center;
            padding: 20px;
        }

        .container {
            background: white;
            border-radius: 20px;
            box-shadow: 0 20px 60px rgba(0, 0, 0, 0.3);
            max-width: 800px;
            width: 100%;
            overflow: hidden;
        }

        .header {
            background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
            color: white;
            padding: 30px;
            text-align: center;
        }

        .header h1 {
            font-size: 2em;
            margin-bottom: 10px;
        }

        .header p {
            opacity: 0.9;
            font-size: 0.95em;
        }

        .tabs {
            display: flex;
            background: #f5f5f5;
            border-bottom: 2px solid #e0e0e0;
        }

        .tab {
            flex: 1;
            padding: 15px;
            text-align: center;
            cursor: pointer;
            background: #f5f5f5;
            border: none;
            font-size: 1em;
            font-weight: 600;
            color: #666;
            transition: all 0.3s;
        }

        .tab:hover {
            background: #ebebeb;
        }

        .tab.active {
            background: white;
            color: #667eea;
            border-bottom: 3px solid #667eea;
        }

        .content {
            padding: 30px;
        }

        .converter-section {
            display: none;
        }

        .converter-section.active {
            display: block;
        }

        .input-group {
            margin-bottom: 20px;
        }

        .input-group label {
            display: block;
            margin-bottom: 8px;
            font-weight: 600;
            color: #333;
        }

        .input-wrapper {
            display: flex;
            gap: 10px;
            align-items: center;
        }

        input[type="number"] {
            flex: 1;
            padding: 12px;
            border: 2px solid #e0e0e0;
            border-radius: 8px;
            font-size: 1em;
            transition: border-color 0.3s;
        }

        input[type="number"]:focus {
            outline: none;
            border-color: #667eea;
        }

        select {
            padding: 12px;
            border: 2px solid #e0e0e0;
            border-radius: 8px;
            font-size: 1em;
            cursor: pointer;
            background: white;
            min-width: 150px;
        }

        select:focus {
            outline: none;
            border-color: #667eea;
        }

        .swap-btn {
            background: #667eea;
            color: white;
            border: none;
            width: 40px;
            height: 40px;
            border-radius: 50%;
            cursor: pointer;
            font-size: 1.2em;
            transition: all 0.3s;
            display: flex;
            align-items: center;
            justify-content: center;
        }

        .swap-btn:hover {
            background: #764ba2;
            transform: rotate(180deg);
        }

        .result {
            background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
            color: white;
            padding: 20px;
            border-radius: 10px;
            margin-top: 20px;
            text-align: center;
        }

        .result-value {
            font-size: 2em;
            font-weight: bold;
            margin-bottom: 5px;
        }

        .result-label {
            opacity: 0.9;
            font-size: 0.9em;
        }

        .history-section {
            margin-top: 30px;
            padding-top: 20px;
            border-top: 2px solid #e0e0e0;
        }

        .history-header {
            display: flex;
            justify-content: space-between;
            align-items: center;
            margin-bottom: 15px;
        }

        .history-header h3 {
            color: #333;
        }

        .clear-btn {
            background: #ff4757;
            color: white;
            border: none;
            padding: 8px 16px;
            border-radius: 6px;
            cursor: pointer;
            font-size: 0.9em;
            transition: background 0.3s;
        }

        .clear-btn:hover {
            background: #ee5a6f;
        }

        .history-list {
            max-height: 200px;
            overflow-y: auto;
        }

        .history-item {
            background: #f9f9f9;
            padding: 12px;
            border-radius: 8px;
            margin-bottom: 8px;
            font-size: 0.9em;
            color: #555;
        }

        .history-empty {
            text-align: center;
            color: #999;
            padding: 20px;
            font-style: italic;
        }

        .error {
            color: #ff4757;
            font-size: 0.85em;
            margin-top: 5px;
        }

        @media (max-width: 600px) {
            .header h1 {
                font-size: 1.5em;
            }

            .input-wrapper {
                flex-direction: column;
            }

            .swap-btn {
                transform: rotate(90deg);
            }

            .swap-btn:hover {
                transform: rotate(270deg);
            }

            .tab {
                font-size: 0.85em;
                padding: 12px 8px;
            }
        }