CSS, with the layout showing

Forty steps through flexbox, twenty-two builds that fail unless several concepts are right at once, and the famous wtfs underneath — margin collapsing, stacking contexts, and the invisible wall inside every flex item. This is the one subject where the output IS the picture, so every problem is rendered rather than described.

Problems

10 problems

All topics Advanced Alignment Distributing space Gap Main axis vs cross axis Making a flex container Order Sizing The famous WTFs The min-width:auto floor Wrapping and the align-content trap

Easy Medium Hard|Teaching step Predict the render Build it Explain the wtf

#	title	topic	type	difficulty
1	display: flex changes the children, not the box	Making a flex container	Teaching step	Easy
2	flex-direction: column swaps which axis is which	Main axis vs cross axis	Teaching step	Easy
3	justify-content is the main axis, align-items is the cross axis	Alignment	Teaching step	Easy
4	align-items: stretch is the default	Alignment	Teaching step	Easy
5	align-self overrides the container	Alignment	Teaching step	Easy
6	justify-content distributes free space — and sometimes there is none	Distributing space	Teaching step	Easy
7	flex-grow distributes the surplus, not the container	Sizing	Teaching step	Easy
8	flex-shrink: 0 is defensive CSS	Sizing	Teaching step	Easy
9	gap spaces items without touching them	Gap	Teaching step	Easy
10	flex-wrap: wrap turns one line into many	Wrapping and the align-content trap	Teaching step	Easy

44 of 87 catalogue topics are authored, with 37 drills rehearsing them. Every one of them is judged: each carries a starter that has been shown to fail, at least two different correct answers that have been shown to pass, and a set of near-misses and cheats that have been shown to be caught. Nothing reaches this list until all of that holds.