body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
    background-color: #f4f7f6;
    color: #333;
    margin: 0;
    padding: 20px;
}
.container {
    max-width: 600px;
    margin: 0 auto;
}
header {
    text-align: center;
    margin-bottom: 30px;
}
header h1 { margin: 0; color: #111; }
.card {
    background: #fff;
    border-radius: 8px;
    padding: 20px;
    margin-bottom: 20px;
    box-shadow: 0 2px 8px rgba(0,0,0,0.05);
}
.balance-card {
    text-align: center;
    background: linear-gradient(135deg, #16a085, #1abc9c);
    color: #fff;
}
.balance-card h2 { margin: 0; font-size: 1.2rem; opacity: 0.9; }
.balance { font-size: 3rem; font-weight: bold; margin: 10px 0; }
.balance small { font-size: 1.2rem; }
.rate-info { font-size: 0.85rem; opacity: 0.8; margin: 0; }
.input-group {
    display: flex;
    gap: 10px;
    margin-top: 15px;
}
input[type="number"] {
    flex: 1;
    padding: 12px;
    border: 1px solid #ccc;
    border-radius: 4px;
    font-size: 1rem;
}
button {
    background: #e67e22;
    color: #fff;
    border: none;
    padding: 12px 20px;
    border-radius: 4px;
    font-size: 1rem;
    cursor: pointer;
    font-weight: bold;
    transition: background 0.2s;
}
button:hover { background: #d35400; }
table {
    width: 100%;
    border-collapse: collapse;
    margin-top: 15px;
    font-size: 0.9rem;
}
th, td {
    padding: 12px;
    text-align: left;
    border-bottom: 1px solid #eee;
}
th { background-color: #fafafa; font-weight: 600; }
.text-center { text-align: center; }
.hidden { display: none !important; }
.result-box {
    background: #e8f8f5;
    border: 2px dashed #2ecc71;
    border-radius: 6px;
    padding: 15px;
    text-align: center;
    margin-top: 20px;
}
.success-msg { color: #27ae60; font-weight: bold; margin: 0 0 10px 0; }
.coupon-code {
    font-family: monospace;
    font-size: 1.6rem;
    font-weight: bold;
    background: #fff;
    padding: 10px;
    display: inline-block;
    border: 1px solid #ddd;
    margin: 10px 0;
    letter-spacing: 2px;
    color: #2c3e50;
}
.notice { font-size: 0.8rem; color: #7f8c8d; margin: 0; }
.error-box {
    background: #fdf2f2;
    color: #c0392b;
    border: 1px solid #f5c6cb;
    padding: 12px;
    border-radius: 4px;
    margin-top: 15px;
    font-size: 0.9rem;
}