html, body {
      margin: 0;
      height: 100%;
      font-family: Arial, sans-serif;
      background-color: #D32C2C;
    }
    header {
      display: flex;
      align-items: center;
      justify-content: space-between;
      background-color: #D32C2C;
      padding: 10px 20px;
      color: white;
      position: fixed;
      top: 0;
      left: 0;
      right: 0;
      z-index: 1000;
    }
    header img {
      height: 40px;
    }
    .donate-btn {
      background: #ffc107;
      border: none;
      padding: 8px 16px;
      font-size: 14px;
      font-weight: bold;
      border-radius: 6px;
      cursor: pointer;
    }
    .donate-btn:hover {
      background: #e0a800;
    }
    .image-container {
      width: 100%;
      height: 100%;
      display: flex;
      justify-content: center;
      align-items: center;
      overflow: hidden;
      padding-top: 60px; /* space for navbar */
      box-sizing: border-box;
    }
    .image-container img {
      max-width: 100%;
      max-height: calc(100vh - 60px);
      object-fit: contain;
    }
    #certificate {
  width: 1122px;   /* A4 width in px (landscape) */
  height: 793px;   /* A4 height in px */
  margin: 0 auto;  /* Center horizontally */
  padding: 40px;
  box-sizing: border-box;
  display: flex;
  flex-direction: column;
  justify-content: center; /* vertical center */
  align-items: center;     /* horizontal center */
}