I guess this should be und the "high score, etc" section.. but whatever
The scoring and time is done to be 100 percent compatible with the scoring from Emerald Mines. As such it is a bit confusing. The bottom line is that one time is 10 seconds which corresponds to 500 ticks, ie 500 screen refreshes at 20ms intervals, ie 50 frames per second (see bottom of recorded game to confirm your speed.... it will be faster if you use the fast forward key). I think the original game was at 25fps due to the speed of the processor, etc... but I made the assumption it was 50 which has made the game twice as fast !! which actually feels right for a 1024 display, etc.
Now, score.... it is confusing. Each tick is 8 screen refreshes and time (internally) is stored in screen refreshes. Ok, let's call "timeLeft" the number of screen refreshes left, then the equation for score is:
Yep, it is confusing. But it is compatible with Emerald Mines and the main reason for writing bd4 was to find more competition for my level set. One of the keys was 100% compatibility. It's basically that except the random number generator which is based on statistics from the ROM Chip rather than the actual ROM data itself
So, one tick is 8 screen refreshes (160ms) and 1 time is 10 seconds. Indeed 1 time is 10000/160=62.5 seconds. It does lead to some confusion but it's how it was meant to be. At least I've changed the main exit time from (for example) 9 meaning 9 time units or part of to "8:100" which means 8 full units and "100" bits/refreshes. It does mean that old scores which had times of, say "0:200" and read "1" now read "0+" in the high scores.