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A typographic specimen book of 한글 — King Sejong's 1443 invention, re-read through the eyes of a developer who has spent years thinking about ligatures, vertical metrics, OpenType features, and the geometry of consonant-vowel composition. Nine leaves follow.

A hangul syllable is a square: an initial consonant atop or beside a medial vowel, optionally closed by a final consonant below. The block is the unit of meaning; the jamo are the unit of letter. Every syllable obeys this geometry — there are no ligature surprises, only twenty-eight rules of arrangement.

function decompose(syllable) {
  const code = syllable.charCodeAt(0) - 0xAC00;
  if (code < 0 || code > 11171) return [syllable];

  const initial = Math.floor(code / (21 * 28));
  const medial  = Math.floor((code % (21 * 28)) / 28);
  const final   = code % 28;

  return [
    INITIALS[initial],
    MEDIALS[medial],
    final ? FINALS[final] : null,
  ].filter(Boolean);
}

// decompose("한") → ["ㅎ", "ㅏ", "ㄴ"]

The Unicode block U+AC00 .. U+D7A3 contains every modern hangul syllable — eleven thousand one hundred seventy-two of them — and each codepoint encodes its three jamo by a deterministic arithmetic. Sejong's geometry, in three lines of integer math.

개발  ·  develop  ·  twenty-eight specimens, the same word in twenty-eight voices.

The fourteen basic consonants, drawn one stroke at a time. Each is a brush movement before it is a letter — hover any glyph to retrace it.

「The round one — empty, like the throat at rest, like a pebble dropped in still water — was made first because the mouth, before it speaks, is silent.」

— after Sejong, Hunminjeongeum Haerye, 1446

Two paths to the same square. The first composes the syllable from conjoining jamo at typesetting time, governed by the OpenType liga and ccmp tables. The second arrives pre-composed, a single Hangul Syllable codepoint. Most fonts ship both — the renderer chooses, and the reader never knows.

A good hangul font hints the vertical metrics of 중성 and 종성 independently, so the syllable block stays optically square across 한, 흙, 뷁. This is the quiet, mathematical beauty Sejong's geometry inherits.