body { font-family: sans-serif; display: flex; justify-content: center; padding: 50px; background-color: #f4f7f6; }
.payment-card { background: white; padding: 2rem; border-radius: 8px; box-shadow: 0 4px 6px rgba(0,0,0,0.1); width: 100%; max-width: 400px; }
.form-group { margin-bottom: 1rem; }
label { display: block; margin-bottom: 0.5rem; font-weight: bold; font-size: 0.9rem; }
input { width: 100%; padding: 10px; border: 1px solid #ccc; border-radius: 4px; box-sizing: border-box; font-size: 1rem; }
.form-row { display: flex; gap: 1rem; }
button { width: 100%; padding: 12px; background-color: #2ecc71; color: white; border: none; border-radius: 4px; font-size: 1rem; cursor: pointer; margin-top: 1rem; }
button:hover { background-color: #27ae60; }
.error { border-color: #e74c3c; background-color: #fdf2f2; }