html,
body {
  width: 100vw;
  height: 100vh;
  margin: 0;
  border: 0;
  padding: 0;
  -webkit-box-sizing: border-box;
  -moz-box-sizing: border-box;
  box-sizing: border-box;
}

*,
*::before,
*::after {
  -webkit-box-sizing: inherit;
  -moz-box-sizing: inherit;
  box-sizing: inherit;
}

#app {
  width: 100%;
  height: 100%;

  font-family: Arial, Helvetica, sans-serif;
}

.resizable-x,
.resizable-y {
  display: flex;
  overflow: hidden;
}

.resizable-x {
  height: 100%;
}

.resizable-y {
  flex-direction: column;
}

.resizer-x,
.resizer-y {
  position: relative;
  display: flex;
  justify-content: center;
  align-items: center;
  background: black;
  padding: 4px;
}

.resizer-x {
  z-index: 2;
  cursor: col-resize;
}
.resizer-x::before,
.resizer-x::after {
  content: "";
  width: 2px;
  height: 16px;
  margin: 2px;
  background: lightgray;
}

.resizer-y {
  z-index: 1;
  cursor: row-resize;
  flex-direction: column;
}
.resizer-y::before,
.resizer-y::after {
  content: "";
  width: 16px;
  height: 2px;
  margin: 2px;
  background: lightgray;
}

.div0,
.div1,
.div2 {
  overflow: hidden;
}

.div0 {
  background: dodgerblue;
  container-type: inline-size;
}

.div1 {
  background: pink;
}

.div2 {
  background: gold;
}

.div0 p,
.div1 p,
.div2 p {
  font-size: 1.2rem;
  margin-left: 1em;
  text-transform: uppercase;
  text-overflow: ellipsis;
  white-space: nowrap;
  overflow: hidden;
}

.child {
  background: gold;
  margin: 12px;
  padding: 8px 8px 8px 8px;
  height: 48px;
  border-radius: 3px;
}

@container (min-width: 400px) {
  .child {
    margin: 48px;
    padding: 8px 16px 8px 16px;
    max-width: 450px;
    background: greenyellow;
  }
}