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

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

.payment-container {
    background: white;
    border-radius: 20px;
    box-shadow: 0 20px 40px rgba(0, 0, 0, 0.1);
    padding: 30px;
    width: 100%;
    max-width: 400px;
    text-align: center;
}

h1 {
    color: #333;
    margin-bottom: 30px;
    font-size: 24px;
    font-weight: 600;
}

.amount-buttons {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 15px;
    margin-bottom: 25px;
}

.amount-btn {
    background: #f8f9fa;
    border: 2px solid #e9ecef;
    border-radius: 15px;
    padding: 20px;
    font-size: 18px;
    font-weight: 600;
    color: #333;
    cursor: pointer;
    transition: all 0.3s ease;
    touch-action: manipulation;
}

.amount-btn:hover {
    background: #667eea;
    color: white;
    border-color: #667eea;
    transform: translateY(-2px);
}

.amount-btn.selected {
    background: #667eea;
    color: white;
    border-color: #667eea;
}

.custom-amount {
    margin-bottom: 25px;
}

.custom-amount input {
    width: 100%;
    padding: 15px;
    border: 2px solid #e9ecef;
    border-radius: 15px;
    font-size: 16px;
    text-align: center;
    outline: none;
    transition: border-color 0.3s ease;
}

.custom-amount input:focus {
    border-color: #667eea;
}

.pay-btn {
    width: 100%;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    color: white;
    border: none;
    border-radius: 15px;
    padding: 18px;
    font-size: 18px;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.3s ease;
    touch-action: manipulation;
}

.pay-btn:hover {
    transform: translateY(-2px);
    box-shadow: 0 10px 20px rgba(102, 126, 234, 0.3);
}

.pay-btn:disabled {
    opacity: 0.6;
    cursor: not-allowed;
    transform: none;
}

.status {
    margin-top: 20px;
    padding: 15px;
    border-radius: 10px;
    font-weight: 500;
}

.status.success {
    background: #d4edda;
    color: #155724;
    border: 1px solid #c3e6cb;
}

.status.error {
    background: #f8d7da;
    color: #721c24;
    border: 1px solid #f5c6cb;
}

.status.loading {
    background: #fff3cd;
    color: #856404;
    border: 1px solid #ffeaa7;
}

@media (max-width: 480px) {
    .payment-container {
        padding: 20px;
        margin: 10px;
    }
    
    h1 {
        font-size: 20px;
    }
    
    .amount-btn {
        padding: 15px;
        font-size: 16px;
    }
}