html, body {
    height: 100%;
    margin: 0;
  }
  body {
    display: flex;
    flex-direction: column;
  }
  main, .container {
    flex: 1 0 auto; /* biar area konten tumbuh */
  }
  footer {
    flex-shrink: 0; /* biar footer gak mengecil */
  }