a fun kind of reverse engineering tactic that I practice probably more than I should is a version of The Scream Test (which is the principle that the easiest way to find who "owns" a server is to turn it off and see who screams): if you don't know what some code does, break it. and see what screams.

I think I may have found unused graphics for a feature that'd change the Acme Detective Agency at the beginning to be season-specific. There's summer, fall, winter, and spring variants, but the game seems to be hardcoded to summer

no, this should be working. Hmm. Maybe they just missed one of the four images?

nope! it's fully functional, based on the system date.

I did a little looking into the contents of MIDISND.DAT

It's got 12 small tracks, and each of them is a valid MIDI file if you remove the first byte.

heh. I was checking different near-death animations by overriding the randomness, so I had to tell my debugger to set AX to 0

guess which animation that is? The one with the AXe.

why do they store the day of the week as a 16bit int?

future proofing in case the calendar gets updated and has more than 256 days in the week?

I accidentally applied a patch backwards and put the detective to sleep, forever.
They're in Rome and they've just slept through about two months of nothing

patching 0x148C9 in the EXE to 90 90 will stop the clock advancing, so you now have Infinite Time to catch the culprit

I finally figured out how it calculates travel times.
It's the difference in X coordinate between the two cities, plus the difference between the Y coordinate, plus one.
that quantity divided by 40, then has 2 added. if the result is over 7, it's set to 7.

Weird! that's not how you measure distance, Carmen.

TODO: plot all the distances between all 30 cities and compare how inɐccurate this mess is

also, it's the 90s, I can afford a sqrt().
I should fix it up for my version.

or use a squared lookup table. you could do this REAL easy by making it a table search: there's only 6 possible results: 2,3,4,5,6,7. each entry in the lookup table contains the maximum squared distance that can generate that number of hours

here's all 30 city locations:https://gist.github.com/foone/0992517879877e0e995259d08a0941a7

it's currently way too 6am to do more calculations, though. I'll do that tomorrow

Good news: @modulusshift did the calculations for me!

~ (@modulusshift@digipres.club)

@foone I did it lol https://docs.google.com/spreadsheets/d/e/2PACX-1vTr5GBfUNkxzVN7RoAiMg081ihERAFs93oE_m_1dPj67IxG-pkMQ41zoVVDlK0DJQepfeRe3NcA-9z8/pubhtml hope this answered any questions you had

digipres.club (digipres.club)

I think that says that it doesn't matter much. The biggest error is in the biggest distances, which are all saturated to the max of 7-hours anyway.

PUSH ES
PUSH AX
RETF

why must you hurt me, carmen sandiego?

I'm confused by the graphics detection routines. I thought it was returning 0 for "no graphics" or something, but it turns out 0 means MCGA.
So the GraphicsMode enum goes:
0: MCGA
1: CGA
2: Hercules
3: EGA
4: Tandy
5: VGA
6: ???

I don't think there's any reason why this would support SVGA. It always use 320x200 at a maximum of 256 colors. VGA is more than enough to handle it

being able to do a textual find-replace on VRAM is a weird but occasionally useful ability

I find-replaced the background from palette entry 0 to palette entry

Now I can confirm how big this image is. Previously it was set into a black background, which made it harder