:root {
    --bg: #f6f7fb;
    --card: #ffffff;
    --text: #1f2937;
    --muted: #6b7280;
    --border: #e5e7eb;
    --accent: #4f46e5;
    --correct: #16a34a;
    --wrong: #dc2626;
  }


  body {
    margin: 0;
    font-family: system-ui, -apple-system, Segoe UI, Roboto, Helvetica, Arial, sans-serif;
    background: var(--bg);
    color: var(--text);
    display: flex;
    justify-content: center;
  }


  .container {
    width: min(1200px, 95vw);
    margin: 40px 0;
  }


  header {
    background: var(--card);
    padding: 20px 24px;
    border: 1px solid var(--border);
    border-radius: 14px;
    margin-bottom: 20px;
    box-shadow: 0 4px 12px rgba(0,0,0,0.04);
  }


  h2 {
    margin: 0;
    font-size: 20px;
    font-weight: 700;
  }


  table {
    width: 100%;
    border-collapse: collapse;
    background: var(--card);
    border-radius: 14px;
    overflow: hidden;
    border: 1px solid var(--border);
    box-shadow: 0 4px 12px rgba(0,0,0,0.04);
    table-layout: fixed;
  }


  th {
    background: #f9fafb;
    text-transform: uppercase;
    font-size: 12px;
    letter-spacing: 0.08em;
    color: var(--muted);
  }


  th, td {
    border-bottom: 1px solid var(--border);
    padding: 10px;
    text-align: center;
    overflow: hidden;
  }


  tr:hover td {
    background: #f3f4f6;
  }


  input {
    width: 100%;
    padding: 8px;
    font-size: 14px;
    text-align: center;
    border: 1px solid var(--border);
    border-radius: 8px;
    outline: none;
    transition: 0.15s ease;
    background: #fff;
    box-sizing: border-box;
  }


  input:focus {
    border-color: var(--accent);
    box-shadow: 0 0 0 3px rgba(79,70,229,0.15);
  }


  .feedback {
    margin-top: 4px;
    font-size: 13px;
  }


  .correct {
    color: var(--correct);
    font-weight: 600;
  }


  .wrong {
    color: var(--wrong);
    font-weight: 600;
  }


  .controls {
    display: flex;
    gap: 10px;
    margin-top: 16px;
  }


  button {
    padding: 10px 14px;
    font-size: 14px;
    border: none;
    border-radius: 10px;
    cursor: pointer;
    transition: 0.15s ease;
  }


  button:first-child {
    background: var(--accent);
    color: white;
  }


  button:first-child:hover {
    opacity: 0.9;
  }


  button:last-child {
    background: #e5e7eb;
  }


  button:last-child:hover {
    background: #d1d5db;
  }
  .ad {
    background: var(--card);
    border: 1px solid var(--border);
    padding: 10px;
    border-radius: 10px;
    font-size: 13px;
    font-weight: 600;
    color: var(--accent);
    flex: 1;
    cursor: pointer;
    transition: all 0.2s;
    width: calc(20%-10px);
    margin: 10px 0px 10px 0px;
}
.ad:hover{
    background: var(--bg);
}