The unit test I added with the generated fills failed on its first run, on
exactly the claim it was written to check, so it earned its keep immediately.
The floor was 0.090 — `neutral-900`'s own HSL lightness — reasoning that a
ramp starting at the card surface and climbing could not end up below it.
That confuses HSL lightness with luminance. At one fixed lightness the eye
sees very different brightnesses by hue, because green carries 71% of the
luminance formula and blue only 7%: at L=0.090 a yellow measures 0.0118 and a
blue 0.0061. Every blue-ish untagged note was 1.41x DARKER than the card it
was supposed to match, which on the board reads as a hole rather than as
variety — the opposite of what the whole change is for.
Solved rather than nudged: 0.113 is the lowest floor at which EVERY hue
clears the card surface. The range now measures 1.11-1.71 against the board
against the old 1.06-1.54, so the floor is back where the shipped ramp had it
and the ceiling is higher. Body text 7.8 against the 4.5 it needs, meta 4.6
against 3.0. 338 distinct dark fills.
Two things about the test are worth keeping.
It asserts on LUMINANCE rather than on the lightness that was put in — a test
of the input would have agreed with the bug and passed.
And it now sweeps 40,000 ids rather than 500. The worst case is a HUE, not an
id, and 500 ids reach only 459 of the 2160 hue/level combinations — it caught
this one by luck. 40,000 covers all 2160.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
bvandeusenandClaude Opus 5
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