It's not just about curving the baseline, the glyphs themselves curve according to the user-specified curve radius. Check out the second image/gif with curve optimizations on/off.

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cellular a minute ago | parent | next [-]

I use a circular font I made in inkscape for outputting SVGs to GatorCAM for CNC.

Inkscape lets me adjust kern of each letter because the curve can cause letters to touch.

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ks2048 4 hours ago | parent | prev [-]

What font features enable this? (curious how it is implemented and which software supports it)

	▲	tshaddox 3 hours ago \| parent [-]
		From what I can tell, it's a variable font, where the font developer can declare an axis (in this case "curve," or more likely "CURV") and the font user can control the value of that axis (e.g. via CSS) which controls how the font renders itself. https://developer.mozilla.org/en-US/docs/Web/CSS/Guides/Font... This site demonstrates many highly stylized and artistic variable font axes: https://www.axis-praxis.org/specimens/__DEFAULT__