body {
            font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
            line-height: 1.6;
            color: #333;
            max-width: 800px;
            margin: 0 auto;
            padding: 20px;
            background-color: #f8f9fa;
        }
        .container {
            background-color: #ffffff;
            border-radius: 12px;
            box-shadow: 0 4px 6px rgba(0, 0, 0, 0.1);
            padding: 30px;
            margin-bottom: 20px;
        }
        h1 {
            color: #2c3e50;
            text-align: center;
            margin-bottom: 10px;
        }
        h2 {
            color: #2c3e50;
            border-bottom: 2px solid #3498db;
            padding-bottom: 10px;
            margin-top: 30px;
        }
        .form-group {
            margin-bottom: 20px;
        }
        label {
            display: block;
            margin-bottom: 5px;
            font-weight: bold;
            color: #2c3e50;
        }
        input, select {
            width: 100%;
            padding: 12px;
            border: 2px solid #e1e8ed;
            border-radius: 6px;
            font-size: 16px;
            box-sizing: border-box;
        }
        input:focus, select:focus {
            outline: none;
            border-color: #3498db;
        }
        button {
            background-color: #3498db;
            color: white;
            padding: 12px 24px;
            border: none;
            border-radius: 6px;
            cursor: pointer;
            font-size: 16px;
            margin: 5px;
            transition: background-color 0.3s;
        }
        button:hover {
            background-color: #2980b9;
        }
        .btn-secondary {
            background-color: #95a5a6;
        }
        .btn-secondary:hover {
            background-color: #7f8c8d;
        }
        .result {
            background-color: #e9f7ef;
            border: 1px solid #c3e6cb;
            border-radius: 8px;
            padding: 25px;
            margin-top: 20px;
            text-align: center;
        }
        .tip-display {
            font-size: 2.5em;
            font-weight: bold;
            color: #155724;
            margin: 10px 0;
        }
        .total-display {
            font-size: 2em;
            font-weight: bold;
            color: #2c3e50;
            margin: 10px 0;
        }
        .per-person {
            font-size: 1.3em;
            color: #7f8c8d;
            margin: 10px 0;
        }
        .tip-presets {
            display: grid;
            grid-template-columns: repeat(auto-fit, minmax(120px, 1fr));
            gap: 10px;
            margin: 15px 0;
        }
        .tip-preset {
            background-color: #f8f9fa;
            border: 2px solid #e1e8ed;
            border-radius: 6px;
            padding: 10px;
            text-align: center;
            cursor: pointer;
            transition: all 0.3s;
        }
        .tip-preset:hover {
            background-color: #e9ecef;
            border-color: #3498db;
        }
        .tip-preset.active {
            background-color: #3498db;
            color: white;
            border-color: #3498db;
        }
        .tip-preset .percentage {
            font-size: 1.2em;
            font-weight: bold;
        }
        .tip-preset .description {
            font-size: 0.9em;
            opacity: 0.8;
        }
        .back-link {
            display: inline-block;
            margin-top: 20px;
            color: #3498db;
            text-decoration: none;
            font-weight: 500;
        }
        .back-link:hover {
            text-decoration: underline;
        }
        .info-box {
            background-color: #d1ecf1;
            border: 1px solid #bee5eb;
            border-radius: 8px;
            padding: 15px;
            margin: 15px 0;
        }
        .info-box h3 {
            margin-top: 0;
            color: #0c5460;
        }
        .split-options {
            display: grid;
            grid-template-columns: repeat(auto-fit, minmax(150px, 1fr));
            gap: 10px;
            margin: 15px 0;
        }
        .split-option {
            background-color: #f8f9fa;
            border: 2px solid #e1e8ed;
            border-radius: 6px;
            padding: 10px;
            text-align: center;
            cursor: pointer;
            transition: all 0.3s;
        }
        .split-option:hover {
            background-color: #e9ecef;
            border-color: #3498db;
        }
        .split-option.active {
            background-color: #2ecc71;
            color: white;
            border-color: #2ecc71;
        }
        .calculation-breakdown {
            background-color: #f8f9fa;
            border: 1px solid #dee2e6;
            border-radius: 8px;
            padding: 15px;
            margin: 15px 0;
        }
        .breakdown-row {
            display: flex;
            justify-content: space-between;
            margin: 8px 0;
            padding: 5px 0;
            border-bottom: 1px solid #e9ecef;
        }
        .breakdown-row:last-child {
            border-bottom: none;
            font-weight: bold;
            font-size: 1.1em;
        }
        @media (max-width: 768px) {
            .tip-presets {
                grid-template-columns: repeat(2, 1fr);
            }
            .split-options {
                grid-template-columns: repeat(2, 1fr);
            }
            .tip-display {
                font-size: 2em;
            }
            .total-display {
                font-size: 1.5em;
            }
        }