canvas and computed geometric boundaries for Input/Output in display.

learning again, repetition to improve.

past works of mine: https://arkenidar.com/web/canvas/.

orientation toward:

this in HTML5... -> https://replit.com/@dariocangialosi/circles.

novelty: a boolean function that answers the question of whether a coordinate is inside a "rounded-corners" boundary.
this should extend-and-include the drawing functionality (produce visual *output* for user)
to "touch in boundary" check also (user *input* checks).