body {
    font-family: Arial, Helvetica, sans-serif;
    background: #f4f4f4;
    margin: 0;
    padding: 20px;
    color: #333;
}

.container {
    max-width: 960px;
    margin: 0 auto;
    background: #fff;
    padding: 30px;
    border-radius: 10px;
    box-shadow: 0 0 20px rgba(0,0,0,0.1);
}

h1 {
    text-align: center;
    color: #444;
}

button {
    background: #007bff;
    color: white;
    border: none;
    padding: 15px 30px;
    font-size: 18px;
    border-radius: 8px;
    cursor: pointer;
    transition: all 0.3s;
}

button:hover:not(:disabled) {
    background: #0056b3;
}

button:disabled {
    background: #aaa;
    cursor: not-allowed;
}

.coupon-result {
    margin: 30px 0;
    padding: 20px;
    background: #e7f5ff;
    border-left: 6px solid #007bff;
    font-size: 24px;
    text-align: center;
    border-radius: 8px;
    min-height: 60px;
    animation: fadeIn 0.8s;
}

@keyframes fadeIn {
    from { opacity: 0; transform: translateY(20px); }
    to { opacity: 1; transform: translateY(0); }
}

.loading {
    color: #666;
    font-style: italic;
}

.history {
    margin-top: 40px;
}

.history h2 {
    color: #555;
    border-bottom: 2px solid #eee;
    padding-bottom: 10px;
}

.history ul {
    list-style: none;
    padding: 0;
}

.history li {
    background: #f9f9f9;
    margin: 10px 0;
    padding: 15px;
    border-radius: 8px;
    border: 1px solid #eee;
    font-size: 18px;
}

table {
    width: 100%;
    border-collapse: collapse;
    margin: 20px 0;
}

table th, table td {
    padding: 12px;
    text-align: left;
    border-bottom: 1px solid #ddd;
}

table th {
    background: #f0f0f0;
}

.form-group {
    margin: 15px 0;
}

label {
    display: block;
    margin-bottom: 8px;
    font-weight: bold;
}

input[type=text], input[type=number], input[type=password] {
    width: 100%;
    padding: 10px;
    border: 1px solid #ccc;
    border-radius: 4px;
    box-sizing: border-box;
}

.alert {
    padding: 15px;
    margin: 20px 0;
    border-radius: 4px;
}

.alert-success { background: #d4edda; color: #155724; border: 1px solid #c3e6cb; }
.alert-error { background: #f8d7da; color: #721c24; border: 1px solid #f5c6cb; }

.text-center { text-align: center; }
.mt-20 { margin-top: 20px; }

/* RWD */
@media (max-width: 768px) {
    .container {
        padding: 20px;
        margin: 10px;
    }
    button {
        width: 100%;
        padding: 18px;
    }
    .coupon-result {
        font-size: 20px;
    }
}