A very clever technique of using combinations of flex-basis, asymmetrical flex-grow, or (for Grid) some quirky minmax() magic to generate flexible layout shifts that, in practice, are controlled by their container's size, but do not use media or container queries at all. Useful for sidebars that you want to fall into a stacking context if there isn't enough room, or (and this is very clever) for making grids with a fixed number of columns e.g. a stack unless you can fit exactly three columns of a minimum width, and then it snaps into a grid layout. Super useful!