Imported from nexu-io/open-design (plugins/_official/examples/huashu-annual-letter/SKILL.md). Install upstream with npx skills add nexu-io/open-design --skill huashu-annual-letter. Copyright stays with the author.

Annual Letter · 年度信笺

Produce a single-file, letter-grade HTML deck in the Stripe Annual Letter genre: a published letter you read, not a template you skim. Prose flows in serif paragraphs; numbers live in inline data cards and giant display anchors. The visual system, canvas contract, and navigation runtime are locked by example.html. Start from example.html, replace content only — do not rewrite the design or the script, and never introduce colors or fonts outside this spec.

Adapted from the editorial-longform style (references/design-styles.md, 安静派 · 杂志编辑长文流 / Editorial Longform) of huashu-design by 花叔 (alchaincyf), MIT licensed. Reference lineage: Stripe Annual Letter, Amazon six-page narrative memos, Stripe Press.

Hard spec (locked — violating any line is a regression)

Canvas & scaling

• One <div id="stage"> fixed at 1920 × 1080 px, centered with position: fixed; top: 50%; left: 50%.
• A fit() function scales the stage to the viewport: scale = min(innerWidth / 1920, innerHeight / 1080), applied as translate(-50%, -50%) scale(s), re-run on resize. Letterboxed, never cropped.
• All layout inside the stage uses px (never vw/vh/% for type) — the scaler owns responsiveness.

Slides & navigation runtime (do not rewrite the script)

• Each page is one <section class="slide"> directly inside #stage, with a data-screen-label="01 刊头"-style label (1-indexed).
• Exactly one slide carries .active. No .dark pages in this theme — every page sits on cream paper; rhythm comes from density, not theme flips.
• Keyboard: ←/↑/PageUp previous · →/↓/Space/PageDown next · Home/End first/last. Hash routing #/N (1-indexed) read on load and hashchange, written via history.replaceState. Click: left third back, rest forward. Fixed counter pill bottom-right, key-hint bottom-left.
• Zero external JS, zero build step; the file must open via file:// inside a sandboxed iframe.

Design tokens (in :root, keep the names — re-theme by changing values only)

--paper:        #FBFAF8;                    /* cream paper, every page */
--panel:        #FFFFFF;                    /* data-card surface */
--ink:          #232036;                    /* deep ink text */
--ink-70:       rgba(35, 32, 54, 0.72);     /* prose body */
--ink-45:       rgba(35, 32, 54, 0.46);     /* captions, chrome */
--hairline:     rgba(35, 32, 54, 0.12);     /* all rules */
--accent:       #635BFF;                    /* Stripe purple — the ONLY accent */
--accent-soft:  rgba(99, 91, 255, 0.08);    /* tint panels, quote marks */
--serif:        "Newsreader", "Source Serif 4", "Noto Serif SC", Georgia, serif;
--serif-text:   "Source Serif 4", "Newsreader", "Noto Serif SC", Georgia, serif;
--sans:         "Inter", "Noto Sans SC", -apple-system, sans-serif;

• Fonts via Google Fonts @import: Newsreader (display, incl. italic), Source Serif 4 (prose), Noto Serif SC (CJK serif), Inter, Noto Sans SC.
• All numerals tabular: the shared .num class sets font-variant-numeric: tabular-nums; every metric, year, and display number uses it.
• One accent. Never a second hue, never a gradient, never a dark slide.

Letter chrome (every page)

• Letterhead top strip with hairline rule: publication/company name left (small-caps Inter, letter-spaced, brand word in accent), issue + date right.
• Footer hairline rule: section name left, author/issue meta right. Page numbering lives only in the runtime counter pill — never also printed inside a slide.
• Headings in var(--serif) (Newsreader/Noto Serif SC), weight 500–600 — letters are set elegantly, not boldly; key words get class="hl" (accent), never the whole heading.
• Kicker: small-caps Inter label with a short 44×3px accent bar above section titles.
• Chinese copy uses 「」 quotes; 中英混排 keeps English in Newsreader italic.

Signature devices (the genre — use them, don't substitute)

Layout enumeration (use 5–6 per deck, never one layout everywhere)

cover masthead page · contents letter outline rows · salutation prose opening with drop cap · display-number anchor · prose+cards running text with inline data cards · chart minimal SVG figure · quote full-page citation · metrics-panorama data-card grid with footnote · closing signature page.

Scale & rhythm

• Body prose ≥ 24px (at 1920×1080), headings 64–132px, display numerals 180–280px, chrome labels 14–16px.
• Alternate density: prose page → display-number page → whitespace/quote page. A letter is quiet; resist decorating it.
• At most 3 accent touches per page; whitespace is the composition.

Workflow

1. Clarify once (skip for small edits): letter type, audience, the year's real numbers and 2–4 narrative chapters, tone. One batch of questions.
2. Real content only. Use the user's actual material and real metrics; never lorem ipsum, never invented statistics. Missing data gets an honest <!-- 待用户提供 --> placeholder.
3. Showcase first for ≥5 pages: build the 2 structurally most different pages (cover + prose-with-cards), confirm, then batch the rest.
4. Copy example.html, retitle, swap token values only if the user has a brand, then replace each section's content following the layout enumeration. Keep letterhead/footer chrome and the script intact.
5. Self-check before delivery: arrow through every page; counter and #/N stay in sync; no overflow; prose stays inside the 980px measure; numerals all tabular; grep for leftover placeholders.

Anti-AI-slop checklist (non-negotiable)

• ❌ Bullet lists where prose should flow — this genre speaks in paragraphs.
• ❌ A second accent color, gradients, dark "tech" pages, neon glow.
• ❌ Emoji as icons; inline SVG or plain glyphs (✦ ✓ → ·) only.
• ❌ Chartjunk: grids, legends, 3D, more than one series color.
• ❌ Proportional figures in metrics — tabular numerals everywhere.
• ✅ One detail at 120% (the display number), the rest at 80%.
• ✅ Honest footnotes and sources under every metric panorama.