stroke-order

/stroke-order — Stroke Order Animation Script

Create a stroke order animation video using MulmoCast with KanjiVG SVG data. Each character is displayed in a square canvas with animated stroke-by-stroke drawing.

Data source: KanjiVG (CC BY-SA 3.0)

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Phase 1: Parse Input

Input

• Characters: $ARGUMENTS (e.g., "あいうえお", "abcdefg", "漢字")
• If no characters are given, ask the user

Supported character types

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Phase 2: Generate Script (Automated)

Output directory

SCRIPTS_DIR="${MULMO_SCRIPTS_DIR:-my-scripts}"

Run the generator script

npx tsx .claude/skills/stroke-order/generate_stroke_order.ts "$ARGUMENTS" "${SCRIPTS_DIR}/test_stroke_order_{slug}.json"

For kanji characters, add readings with --readings:

npx tsx .claude/skills/stroke-order/generate_stroke_order.ts "漢字" "${SCRIPTS_DIR}/test_stroke_order_kanji.json" --readings "カン/-,ジ/あざ"

The generator automatically:

1. Fetches KanjiVG SVG data for each character from GitHub
2. Extracts stroke paths in correct order
3. Calculates animation timing based on stroke count
4. Generates the complete MulmoScript JSON

--readings option (for kanji)

Format: "onyomi/kunyomi,onyomi/kunyomi,..." — one entry per character, comma-separated.

• Use - for missing readings (e.g., カン/- = onyomi only)
• Multiple readings separated by ・ (e.g., カン・ガン/みず)

Effects:

• Label: Shows 音 カン and 訓 あざ below the character
• Speech: TTS reads "音読み、カン。訓読み、あざ。" instead of the raw kanji

Without --readings, kanji characters are spoken as-is (may result in unexpected TTS pronunciation).

Output file naming

• Hiragana: test_stroke_order_hiragana_{romaji}.json
• Katakana: test_stroke_order_katakana_{romaji}.json
• Latin: test_stroke_order_alphabet_{first}_{last}.json
• Kanji (with readings): test_stroke_order_{onyomi_romaji}.json (e.g., kan_ji)
• Kanji (without readings): test_stroke_order_{characters}.json (e.g., 漢字)

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Phase 3: Generate Movie

After script generation, immediately run yarn movie (no need for separate yarn audio — all beats have fixed durations, so yarn movie handles audio generation internally).

yarn movie ${SCRIPTS_DIR}/test_stroke_order_{slug}.json

Output: output/test_stroke_order_{slug}_{lang}.mp4

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Technical Details (for reference)

KanjiVG Data

• Repository: https://github.com/KanjiVG/kanjivg
• Raw URL: https://raw.githubusercontent.com/KanjiVG/kanjivg/master/kanji/{5-digit-hex-codepoint}.svg
• Unicode codepoint examples:
  • あ (U+3042) → 03042.svg
  • a (U+0061) → 00061.svg
  • 漢 (U+6F22) → 06f22.svg
• viewBox: 0 0 109 109
• Path IDs: kvg:{codepoint}-s1, kvg:{codepoint}-s2, etc.

Animation Technique

SVG stroke-dasharray / stroke-dashoffset animation:

• Ghost paths: same d attributes with stroke='#9ca3af' (gray-400, always visible)
• Animated paths: stroke='#dc2626' (red-600), stroke-dasharray='400' stroke-dashoffset='400' → animate dashoffset to 0

Stroke Color

All animated strokes use a single color: Red (#dc2626 / red-600).

Duration by Stroke Count

Base duration + 1s extra. First stroke starts 0.5s after beat begins.

Canvas & Layout

• Canvas: 720x720 (square)
• SVG display: 420x420 centered
• Guide lines: center cross with dashed lines
• Character label below SVG: text-5xl for character, text-2xl for romanization (hiragana/katakana), text-xl for onyomi/kunyomi (kanji)
• Background: bg-amber-50 (cream)

Beat Structure

MulmoScript Template

{
  "$mulmocast": { "version": "1.1" },
  "lang": "ja",
  "title": "書き順：ひらがな あ〜お",
  "canvasSize": { "width": 720, "height": 720 },
  "speechParams": {
    "speakers": {
      "Presenter": { "voiceId": "shimmer", "displayName": { "ja": "先生" } }
    }
  },
  "beats": [
    { "id": "intro", "...": "..." },
    { "id": "char_a", "...": "..." }
  ]
}

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Reference

Working examples:

• my-scripts/test_stroke_order_alphabet.json (a-g)
• my-scripts/test_stroke_order_hiragana.json (あ-こ)
• my-scripts/test_stroke_order_kanji.json (漢字, with --readings)