Font smoothing
The same font at the same weight looks bolder in light-on-dark than dark-on-light. The fix is not a thinner weight.
Thin weights thin out further on dark grounds and disappear. So on a dark surface I hold regular weight, or step small text up one weight, rather than pushing contrast to maximum or reaching for 300. Text colour on dark is off-white, around 0.96 in OKLCH lightness, and the secondary and tertiary steps sit closer together than they do in light.
- Below 18px stay at 400 or heavier, on any ground
- Weights under 300 are display-only at 28px and above
- Check on a real display at 1x and 2x; macOS antialiasing settings change the answer
`-webkit-font-smoothing: antialiased` on the body is a preference, not a fix. It makes text lighter on Retina Macs and does nothing anywhere else.