<div class="container">
  <div class="box-wrap">
    <input type="checkbox">
    <div class="box">
      I've got an `auto` height so my height is generally unknown to CSS.
    </div>
  </div>
  
  <div class="box-wrap">
    <input type="checkbox">
    <div class="box">
      I've got also got an unknown height and I've got even more content just to demonstrate how this works for unknown sizes.
    </div>
  </div>
</div>

body {
  height: 100vh;
  margin: 0;
  display: grid;
  place-items: center;
}

.container {
  display: flex;
  align-items: flex-start;
  gap: 2rem;
}

.box-wrap {
  text-align: center;
}

.box {
  width: 200px;
  overflow: clip;
  background: salmon;
  height: calc-size(auto, size);
  transition: 0.2s ease-in-out;
  
  [type="checkbox"]:checked + & {
    height: 0; 
  }
}

.box-2 {
  height: 80px;
}