demo-container { display: block; border: 2px solid rgb(189, 189, 189); padding: 25px 10px 10px; border-radius: 4px; width: 220px; resize: horizontal; overflow: auto; }
demo-object { display: block; background-color: rgb(224, 255, 253); container-name: myContainer; }
.element {container-type: inline-size;}
@container myContainer (width < 300px) {
block-block { width: 50%; border: 2px solid maroon; background-color: salmon; }
}