Xuan Kong Flying Star 玄空飛星 Glossary

A San Yuan system that builds a nine-palace star chart from three inputs — the 20-year period, the sitting mountain and the facing mountain — by "flying" numbers along the fixed Luoshu path.

Xuānkōng fēixīng · 玄空飞星 (simplified) · 玄空飛星 (traditional)

Source credibility (S/A/B/C/X): S A    Rule computability (A/B/C): A

What it is

Xuan Kong Flying Star divides a building's floor plan into the nine palaces of the Luoshu magic square, then places three numbers in each palace: the period star, the mountain star （山星） and the facing star （向星）. The period is taken from the 180-year San Yuan Jiu Yun cycle (see Yun Period); the sitting and facing come from a compass reading expressed in the 24 Mountains. The mountain star governs people and health, the facing star governs wealth — a reading of "water in front, mountain behind" expressed numerically.

The "flying" is a fixed walk through the palaces: centre → Qian (NW) → Dui (W) → Gen (NE) → Li (S) → Kan (N) → Kun (SW) → Zhen (E) → Xun (SE). Whether a star walks forward or backward along this path is decided by the yin/yang of the mountain's elemental dragon class （三元龍）. From the finished chart the tradition names recognisable patterns — Wang Shan Wang Xiang （旺山旺向, prosperous mountain and facing）, Shang Shan Xia Shui （上山下水）, the doubled-star gatherings, Fu Yin and Fan Yin.

School differences

Most of the chart algorithm is stable across lineages, but two joints genuinely move: the replacement-star rule for off-grid readings (see Xia Gua / Ti Gua), where the Shen family lists replacements for all 24 mountains while the Zhongzhou line uses "only thirteen stars", and the handling of the remaining 12 mountains under that rhyme, where two readings produce different charts. The time axis also varies: the Tan Yangwu lineage uses a different "two-element eight-period" division (see Yun Period). Different schools define these differently; the disagreement lives in the tradition, not in a bug — see the School Dispute Register, entries D-03 and D-06.

How this engine computes it

• The seven-step lower-trigram chart algorithm is implemented as specified in the project's rule tables, including the fixed forward-flying trajectory and the yin/yang decision per elemental-dragon class; worked examples (Period 7 Zi sitting / Wu facing, Period 8 Wu / Zi) were reproduced during collation.
• All 5,184 period-sitting-facing charts are replayed against the project's golden set as part of the verification suite.
• Replacement charts follow the unified threshold — lower-trigram zone ±4.5° around each mountain centre, replacement zone 3° on each side (4.5°–7.5°) — and the two documented replacement variants; the selected variant is recorded in ruleset_id and shown side by side where they disagree.
• The period boundary is the Lichun instant, shared with the year-pillar engine — not January 1st.

Related entries

24 Mountains · Xia Gua / Ti Gua · Yun Period · Nine Stars · San Yuan vs San He

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