:root {
    --bg:#f6f7fb;
    --card-bg:#273043;
    --card-accent:#f36d21;
    --card-text:#fff;
    --muted:#7a7f8a;
  }
  
  * { box-sizing:border-box; }
  
  body {
    font-family: system-ui, -apple-system, "Segoe UI", Roboto, "Helvetica Neue", Arial;
    background: var(--bg);
    margin: 0;
    padding: 32px;
    color: #111;
  }
  
  .container {
    max-width: 920px;
    margin: 0 auto;
  }
  
  h1 {
    margin: 0 0 18px 0;
    font-size: 1.4rem;
  }
  
  form {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 20px;
    align-items: start;
  }
  
  @media (max-width:800px) {
    form { grid-template-columns: 1fr; }
  }
  
  .card-visual {
    display: grid;
    grid-template-rows: auto auto;
    gap: 18px;
  }
  
  .card {
    border-radius: 14px;
    padding: 18px;
    color: var(--card-text);
    min-height: 140px;
    position: relative;
    overflow: hidden;
    box-shadow: 0 8px 18px rgba(10,20,30,0.12);
  }
  
  .card-front {
    background: linear-gradient(135deg,#334559 0%, #233444 100%);
  }
  
  .card-back {
    background: linear-gradient(180deg,#222831 0%, #1b2228 100%);
  }
  
  .chip {
    width: 44px;
    height: 30px;
    border-radius: 4px;
    background: linear-gradient(180deg,#e6e0b3,#bfae5a);
    box-shadow: inset 0 -2px 0 rgba(255,255,255,0.2);
    margin-bottom: 12px;
  }
  
  .card-number {
    font-family: "Courier New", monospace;
    letter-spacing: 2px;
    font-size: 1.05rem;
    margin-bottom: 12px;
  }
  
  .card-row {
    display: flex;
    justify-content: space-between;
    align-items: center;
  }
  
  .card-name,
  .card-exp {
    font-size: 0.88rem;
    color: rgba(255,255,255,0.9);
  }
  
  .mag-strip {
    height: 36px;
    background: #111;
    margin-top: 12px;
    border-radius: 4px;
  }
  
  .signature-area {
    display: flex;
    justify-content: flex-end;
    align-items: center;
    padding-top: 14px;
  }
  
  .sig-label {
    font-size: 0.75rem;
    color: var(--muted);
    margin-right: 8px;
  }
  
  .cvv-visual {
    background: #fff;
    color: #111;
    padding: 6px 8px;
    border-radius: 4px;
    font-weight: 600;
    min-width: 36px;
    text-align: center;
  }
  
  .form-fields {
    padding: 12px;
    background: #fff;
    border-radius: 12px;
    box-shadow: 0 6px 14px rgba(12,18,26,0.06);
  }
  
  .field { margin-bottom: 12px; }
  
  .field label {
    display: block;
    margin-bottom: 6px;
    font-size: 0.85rem;
    color: var(--muted);
  }
  
  .field input,
  .field select {
    width: 100%;
    padding: 10px 12px;
    border-radius: 8px;
    border: 1px solid #dde1e9;
    font-size: 0.95rem;
  }
  
  .row {
    display: flex;
    gap: 12px;
  }
  
  .small { flex: 1; }
  
  .exp-row {
    display: flex;
    gap: 8px;
  }
  
  .errorMsg {
    color: #b00020;
    min-height: 1.2em;
    margin: 8px 0;
  }
  
  .successMsg {
    color: green;
    min-height: 1.2em;
    margin: 8px 0;
    font-weight: 600;
  }
  
  .submit-btn {
    display: inline-block;
    margin-top: 6px;
    background: var(--card-accent);
    color: white;
    padding: 10px 16px;
    border-radius: 10px;
    border: 0;
    font-size: 1rem;
    cursor: pointer;
  }
  
  .submit-btn:active {
    transform: translateY(1px);
  }