e: vertical-lr;
}
html { block-size: 40vw; }

.b {
  inline-size: 50vh;
  block-size: 210vw;
  box-sizing: border-box;
  border: 5px solid black;
  border-block-start-color: blue;
  border-inline-start-color: lime;
  margin-inline-start: 20px;
  margin-block-end: -20px;
}
</style>
<body>
  <div class="b"></div>
</body>
</html>
