Design System
IO uses Apple's SF Pro font system via system font stack.
-apple-system, BlinkMacSystemFont, "SF Pro Display", "SF Pro Text", "Helvetica Neue", sans-serif
.text-hero (80px/700), .text-display (56px/700), .text-title1 (48px/700), .text-title2 (28px/700), .text-title3 (21px/600), .text-headline (17px/600), .text-body (17px/400), .text-subhead (15px/400), .text-footnote (13px/400), .text-caption (12px/400), .text-label (11px/500 uppercase)
Hero/Display -0.003em (tight), Body -0.022em (Apple standard), Labels 0.06em (wide for uppercase)