In-browser stenotype demo using normal/qwerty keyboard.

"In a 2D top-down map it is sometimes useful to calculate which areas are visible from a given point. For example you might want to hide what’s not visible from the player’s location, or you might want to know what areas would be lit by a torch."

See also Nicky Case's similar "Sight and Light":
https://ncase.me/sight-and-light/

Steve Losh's post on why and how he uses vim.