:root { --primary: #2c3e50; --accent: #2980b9; --bg: #f4f7f6; }
        body { font-family: "Helvetica Neue", Arial, sans-serif; background-color: var(--bg); padding: 20px; color: #333; line-height: 1.6; }
        .container { max-width: 800px; margin: 0 auto; background: white; padding: 30px; border-radius: 15px; box-shadow: 0 5px 15px rgba(0,0,0,0.08); }
        h1 { text-align: center; color: var(--primary); font-size: 1.6rem; border-bottom: 2px solid var(--primary); padding-bottom: 15px; margin-bottom: 30px; }
        
        .form-section { border: 1px solid #eee; padding: 20px; border-radius: 10px; margin-bottom: 20px; background: #fafafa; }
        .section-title { font-weight: bold; color: var(--primary); margin-bottom: 15px; display: block; border-left: 4px solid var(--primary); padding-left: 10px; }
        
        .form-grid { display: grid; grid-template-columns: 1fr 1fr; gap: 20px; }
        .form-group { display: flex; flex-direction: column; }
        label { font-size: 0.85rem; font-weight: bold; margin-bottom: 5px; color: #555; }
        input, select { padding: 12px; border: 1px solid #ccc; border-radius: 8px; font-size: 1rem; }
        
        .calc-btn { width: 100%; padding: 18px; background: var(--primary); color: white; border: none; border-radius: 8px; font-size: 1.2rem; font-weight: bold; cursor: pointer; margin-top: 10px; transition: 0.3s; }
        .calc-btn:hover { background: #34495e; transform: translateY(-1px); }

        .result-box { margin-top: 30px; display: none; background: #fff; border: 2px solid var(--primary); border-radius: 10px; overflow: hidden; }
        .result-header { background: var(--primary); color: white; padding: 12px; text-align: center; font-weight: bold; }
        .result-body { padding: 25px; text-align: center; }
        .amount-display { font-size: 2.2rem; font-weight: bold; color: #e67e22; margin: 10px 0; }
        .amount-display span { font-size: 1rem; color: #333; margin-left: 5px; }

        .note { font-size: 0.8rem; color: #777; background: #fff; padding: 15px; margin-top: 20px; border-radius: 8px; border: 1px solid #ddd; }

        /* モバイル対応（スマホ表示） */
        @media screen and (max-width: 600px) {
            .container { padding: 20px; }
            .form-grid { grid-template-columns: 1fr; }
            h1 { font-size: 1.3rem; }
            .amount-display { font-size: 1.8rem; }
        }