The amber arc was drawn at radius ~30px from center on a 56×56
canvas — the bottom of the arc (at angles near 6 o'clock) sat at
y ≈ 58 and got clipped by the canvas's own bounding box. Visible
as a flat cut-off at extreme positions.
Fix: bump the canvas to 72×72 and use fixed-pixel values for the
knob's geometry instead of fractions of `size`, so the visible knob
diameter stays at ~52px regardless of canvas size and there's now
~10px of margin all around for the arc and drop shadow.
- KNOB_SIZE: 56 → 72
- totalR: size * 0.46 → 26 (fixed)
- rimW: size * 0.045 → 2.5 (fixed)
- notch half-base: size * 0.026 → 1.5 (fixed)
- cy: size/2 + 1 → size/2 (no need for the offset on the larger canvas)
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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