I implemented time bonus. Each second not used from an allocated 10s per level is now counted as score.
How to keep track of seconds on an Apple II? With the mouse interrupts, which come at 60 or 50Hz depending on the country.
How to know the frequency of the interrupts? Easy, calibrate by counting the number of loops between two mouse interrupts.
Commit: https://github.com/colinleroy/a2tools/commit/1a4fc760c12f27d3c25bbc26ece4ca3f7aad3f74