Used by the routine at READ_LINE.

Counts down from PATIENCE while it scans the keyboard, and returns the first new key. If the count runs out first it does something rather nice: it clears the line, copies the four letters at WAIT_TEXT -- WAIT -- into it, prints them, and returns a carriage return as though the player had pressed ENTER. So "time passes" is the game typing a command on your behalf, and the WAIT lines on screen that nobody typed are exactly that.

The keyboard scan reports only changes. A driver that stops the game with ENTER held and presses it again at the next prompt is not heard, because the release was never seen; hobbit_drive.py lets it scan with nothing held first.