Black emits no light, so it reads as fully transparent. Any surface you need to see has to sit above it. Note the first swatch below that is actually visible on your glasses, and use that as your floor for cards and headers.
Heading 1 — 28dp bold
Heading 2 — 22dp bold
Body 1 — 16dp regular. This is the size most of your interface copy should use.
Body 2 — 14dp regular. The floor for anything interactive.
Meta 1 — 12dp regular. Labels and timestamps only.
Meta 2 — 10dp regular. Rarely legible in bright surroundings.
Read this outdoors and indoors. The size that fails in sunlight is your real floor, not the size that fails at a desk.
Safe area
Count the corner marks you can see. Any that are missing are being clipped, so keep interactive elements inside the inner box.
Every key is logged. Swipe to move focus between the pad and Done, then pinch Done to exit. If a back-gesture line never appears, this device does not deliver Escape.