A structured lesson workspace with readable content, hands-on examples, and a clean path to completion.
<style>.demo { justify-content: space-between; }</style><main class="demo">Example content</main>
In production, align-content only matters when there is extra cross-axis space and multiple flex lines. It does nothing for a single-line flex container. That is the kind of bug that survives visual spot checks because the stylesheet is syntactically valid while the layout contract is wrong.
The useful mental model here is practical: how justify-content, align-items, align-content, and gap distribute available space. When a rule looks obvious but the browser produces something else, start by identifying which constraint or rendering phase is actually winning.
<style>.demo { align-items: stretch; }</style><main class="demo">Example content</main>
Engineering judgment: Use gap for consistent item separation. Use distribution properties when the relationship is about available free space rather than fixed spacing.
| Concern | What to inspect | Typical failure |
|---|---|---|
| Core behavior | Alignment and Distribution | align-content only matters when there is extra cross-axis space and multiple flex lines. It does nothing for a single-line flex container. |
| Production test | Real content and constraints | The rule works only for the demo values |
| Maintenance | Scope and override path | A later fix creates another exception |
The useful mental model here is practical: how justify-content, align-items, align-content, and gap distribute available space. When a rule looks obvious but the browser produces something else, start by identifying which constraint or rendering phase is actually winning.
<style>.demo { align-content: start; }</style><main class="demo">Example content</main>
Multi-line rows is useful here because it demonstrates alignment and distribution under a concrete input rather than as an abstract property list.
<style>.demo { gap: 1.25rem; }</style><main class="demo">Example content</main>
Uniform gap is useful here because it demonstrates alignment and distribution under a concrete input rather than as an abstract property list.
Finish the lesson once you have worked through the material. This awards ★ 30 XP.