Penrose tiling in SQL

pt.sql

-- requires SQLite ver.3.34.0 or later

-- ref. How to construct Penrose tilings
-- https://tartarus.org/~simon/20110412-penrose/penrose.xhtml

WITH consts AS (
  SELECT
    8 AS n,                      -- number of iterations
    500 AS l,                    -- width & height of image
    0.7265425280053609 AS tan36, -- tan(π/5)
    0.6180339887498948 AS d      -- 1/φ
), tiles (i, t, px, py, qx, qy, rx, ry) AS (
  SELECT n, 1, -l/tan36, 0, 0, l, l/tan36, 0 FROM consts
  UNION ALL
  SELECT i-1, 0, rx, ry, px*(1-d)+qx*d, py*(1-d)+qy*d, qx, qy
    FROM tiles, consts WHERE t = 0 and i > 0
  UNION ALL
  SELECT i-1, 1, rx, ry, px*(1-d)+qx*d, py*(1-d)+qy*d, px, py
    FROM tiles, consts WHERE t = 0 and i > 0
  UNION ALL
  SELECT i-1, 1, px*(1-d)+rx*d, py*(1-d)+ry*d, px*(1-d)+qx*d, py*(1-d)+qy*d, px, py
    FROM tiles, consts WHERE t = 1 and i > 0
  UNION ALL
  SELECT i-1, 0, px*(1-d)+rx*d, py*(1-d)+ry*d, px*(1-d)+qx*d, py*(1-d)+qy*d, qx, qy
    FROM tiles, consts WHERE t = 1 and i > 0
  UNION ALL
  SELECT i-1, 1, rx, ry, px*(1-d)+rx*d, py*(1-d)+ry*d, qx, qy
    FROM tiles, consts WHERE t = 1 and i > 0
)
SELECT printf('<svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" width="%d" height="%d" viewBox="%d %d %d %d"><g id="t">',
              l, l, -l/2, -l/2, l, l)
  FROM consts
UNION ALL SELECT
  printf('<g stroke="#044a64" stroke-width="0.3" stroke-linejoin="bevel" fill="%s">%s</g>',
    CASE t WHEN 0 THEN '#044a64' ELSE '#fff' END,
    group_concat(printf('<path d="M%f %fL%f %fL%f %fz"/>', px, py, qx, qy, rx, ry), char(10))
  )
  FROM tiles WHERE i = 0 GROUP BY t
UNION ALL SELECT '</g><use xlink:href="#t" transform="scale(1 -1)"/></svg>';

pt.svg