One published component, five axes, twenty-four variants - and the clearest example in the kit of why something becomes a variant rather than a hidden layer.
One component, twenty-four variants
Card - Size × Show Header × Show Action × Show Footer × Show Image: default · sm × Yes · No on each of the four parts, less the eight where an action has no header to sit in
Using the Card
Why is the action an axis when it does not change the height?
Because it changes the width of the thing beside it. The title block is 388 wide with no action and 316 with one, and hiding a layer leaves its sibling at the old width. Only a variant can resize a neighbour, which is the real rule - not whether the outer box grows.
Why 24 and not 32?
Two sizes times four switches is 32, but Show Action only exists when Show Header does. An action with no header is a button floating over the content, so those eight are not drawn.
What is the difference between default and sm?
Three of the four parts get tighter: content 76 to 72, header 80 to 68, footer 92 to 84. The image stays at 262 in both, because a smaller card is not a reason for a smaller photograph. Every height in the file is a sum of those four numbers.
Why does the footer have its own colour?
It is filled at #FAFAFA with a 1px top border, while the header and content sit on the card's plain white. That makes the footer read as a shelf under the content rather than more of the same surface - it is the only part of the card that changes ground.