/.metanomicon · The phase disc

Evidence

Built directly. Harness: probe-cf.mjs (shared with the address stratum), results in probe-cf.json. Playwright/Chromium, --use-gl=swiftshader.

What it is

The ephemeris draws the moon through the dither gate: a 0..1 quantity as the lit fraction of a disc with a real terminator (an ellipse, not a straight edge), a limb that falls away, Bayer-8 deciding every cell. phaseDisc(cv, q, N) is that routine with the phase solved from the quantity on the waxing branch — phase = acos(1 − 2q) / 2π — so any 0..1 value is read the way the moon is read. Same value, same pixels.

Three instruments, no fourth

instrument	quantity	where
the reader's position	page progress 0..1	the rail, beside `scroll 0.412`
the machine's state	field scale ÷ display cap	the rail foot, beside `field ×1.00`
the reader's control	(gate gain − 0.8) ÷ 0.8	the gate, beside the slider's output

A primitive, not a motif. The fourth use would be the one that turns it into decoration, and the copy says so where the primitive is defined.

Measured

discs on the page                      3
cells per disc / CSS size              28 / 14 px, image-rendering: pixelated
reader's disc at top / at mid-page     q 0.000 / 0.516
control's disc at gain 0.80 / 1.60     q 0.000 / 1.000
machine's disc, settled                q 1.000 (software GL held full scale at 1440×900)
grey pixels in the moon canvas         0 of 669 lit   (every lit pixel is rgb(226,228,230) at alpha 255)
grey pixels in the rail disc           0
console errors                         0

Not established

Pixel identity between phaseDisc at N = 52 and the ephemeris's drawMoon at the same phase. They are the same routine copied, with the phase solved rather than given, and both probes show zero greys and witness-only ink — but the moon is scoped inside the ephemeris IIFE and was not rendered through the shared function in this probe. Structural identity, not a byte compare.
Legibility of a 14 px disc as an instrument at arm's length. It is a glyph-sized object; whether a reader parses a quarter from a half at that size was not tested.