[semiinfinitely]

so how do you type a number?

[numpad0]

They use special "upper" and "lower" layer keys to switch between mappings. There's a whole open source ecosystem around a project called QMK firmware, and convergent common keymaps for keyboards that use it.

1: https://github.com/qmk/qmk_firmware

[nagaiaida]

with a numpad but without moving my hand