Vertical 3:4 Layout Skill

This skill is the layout source of truth for vertical-3-4 pages, usually 1200x1600.

A 3:4 page is a vertical poster-card canvas. It has enough width for rich information cards and compact two-column pockets, but its reading path is still vertical. The layout should feel like a poster with one strong anchor and grouped evidence, not a long feed of equal blocks.

This canvas is a poster card, not a compressed slide. When the source content is dense or "needs to be summarized", the model MUST summarize harder here, not cram the full outline into one page. A 3:4 poster that tries to hold a 16:9 deck's worth of content will overflow no matter how the fonts are tuned.

Deep details live in the references:

• references/catalog.md - named poster-card patterns and 1200x1600 zone skeletons.
• references/checklist.md - P0/P1/P2 structural self-check for delivery.

Preflight

Before writing HTML, decide:

1. Message - the one sentence this card should make the viewer remember.
2. Focal anchor - title block, hero metric, chart, image/diagram, framework, or conclusion.
3. Support groups - hard cap 3-4 support bands (or 5-6 compact rows/chips for grouped facts). Anything beyond MUST be cut, merged, or repackaged as one hero object — never squeezed in by shrinking fonts.
4. Reading path - top claim -> main proof/value -> bottom synthesis/source.
5. Density - low-medium for poster claims, medium for most information cards, high only for compact lists or matrices. Never use "high density" as a reason to exceed the 4-band cap.
6. Pattern - choose one structure from references/catalog.md before writing HTML.
7. Budget - estimate hero zone, main proof zone, bottom synthesis, gaps, and reserve.

Use the canvas dimensions from the prompt. If custom dimensions are supplied, preserve the same vertical poster relationships.

Canvas Grammar

• Keep one visual or conceptual anchor larger than the rest.
• Use vertical sections, but group small facts into bands, rows, or chips so the card does not become a long list.
• A compact two-column pocket is allowed inside one section when each item remains readable.
• Let the bottom carry synthesis, implication, source, or a final evidence band.
• Use grid/flex document flow for text-bearing modules. Absolute positioning is only for background accents, connector lines, and non-text decoration.
• Capacity ceiling (hard): per page = 1 focal anchor + up to 4 support bands (or 6 compact rows/chips) + 1 bottom synthesis. A "band" is a labeled section, a comparison row group, an evidence cluster, or a step group — not a single bullet. If the outline gives you more points than this ceiling, the page agent resolves overload IN-PAGE by compressing/merging/rewriting into fewer denser bands; never by shrinking font below the floors, never by splitting into multiple pages.
• Vertical fill (hard): the page must use the full canvas height with no accidental top-stack or bottom gap. The main content wrapper MUST be flex flex-col with at least one flex-1 / flex-grow child absorbing leftover height (typically the support group or the bottom synthesis), OR use justify-between to spread focal / support / synthesis across the canvas. Never set fixed top padding (pt-[NNpx]) and let content stack from the top while the bottom is empty. If content is shorter than the canvas, the flex-1 block expands; if longer, you have exceeded the capacity ceiling — compress.
• Body copy, ordinary labels, and card descriptions must be at least 32px (Tailwind text-3xl is 30px — too small, use text-[32px] or style="font-size:32px"); headings must be at least 43px (text-[43px] or larger, text-4xl/text-5xl); auxiliary source/footer text must be at least 21px (text-[21px] or text-xl). These floors compensate for the much smaller fit-scale a 1600h canvas gets on a landscape presentation screen — default text-lg/text-xl (18px/20px) will be unreadable, do not use them on this canvas.

Pattern Quick Lookup

Use references/catalog.md for the full structure recipe before writing a new or heavily repaired card.

Poster Budget

Calculate before writing:

1. Canvas height: usually 1600px.
2. Outer vertical padding: commonly 72-128px total.
3. Hero/title zone: usually 240-420px depending on focal scale.
4. Gaps between sections.
5. Bottom conclusion/source/reserve: 80-240px when present.
6. Remaining height is the main proof/value zone.

Canvas width is usually 1200px. After horizontal padding, use one full-width column or one compact two-column pocket.

For charts, reserve a specific frame height and keep the @ppt-chart-height=N marker aligned with the h-[Npx] class. Prefer one clear chart, hero metric, compact bars, rank list, or short table.

Repair And Self-check

• If the card is just a stack of cards, introduce a hero/focal block.
• If the bottom is empty, add synthesis, implication, source, or a final evidence band.
• If there are too many small facts, group them into bands or chips under shared labels.
• If the outline oversupply exceeds the 4-band ceiling, resolve overload in this priority: (1) summarize and compress — say the same information in fewer words (long descriptions become short phrases, sentences become single data points; remove water, not information), (2) merge related points into one band with a shared label, (3) rewrite a long list as one hero metric + one-line interpretation, (4) switch pattern to a denser format (e.g. comparison rows, ranked chips). Never resolve overload by going below the font floors or by exceeding the canvas height.
• If a two-column pocket feels cramped, return to full-width rows.
• If a chart/table is hard to read, convert it to a hero metric, rank list, compact bars, or grouped rows.
• Before delivery, run references/checklist.md.