* {
      margin: 0;
      padding: 0;
      box-sizing: border-box;
    }
body {
    font-family: Arial;
    display: flex;
  /*  flex-direction: row;*/
    min-height: 100vh;/*1vh = 1/100 chiều cao view*/
    background: #f4f4f4;
}
.leftbar {
    width: 250px;
    background-color: #2c3e50;
    color: white;
    padding: 1rem;
}
.leftbar h2 {
    margin-bottom: 2rem;
}
.leftbar a {
    display: block;
    color: white;
    text-decoration: none;
    margin-bottom: 16px;
}
.leftbar a:hover {
    text-decoration: underline;
    color: yellow;
}
.main {
    flex-grow: 1;
    padding: 2rem;
}
    .cards {
      display: grid;
      grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
      gap: 1rem;
    }
    .card {
      background: white;
      padding: 1.5rem;
      border-radius: 8px;
      box-shadow: 0 0 10px rgba(0,0,0,0.1);
    }
    .card h3 {
      margin-bottom: 0.5rem;
    }
    table {
      width: 100%;
      border-collapse: collapse;
      margin-top: 2rem;
    }
    table th, table td {
      padding: 0.75rem;
      text-align: left;
      border-bottom: 1px solid #ccc;
    }
    table th {
      background-color: #ecf0f1;
    }