Posted By
TCFS
on 2022-07-28
16:22:16
 |  Re: Impossible Mission +4
Just to be clear. Nothing was reused from the original code. Nothing from the memory dump of the original game. Even the graphical elements were "grabbed" using my rotoscopy tool from screenshots and not converted from original charsets. (Mainly using screenshots downloaded from the "Rooms" section of this page: https://www.c64-wiki.com/wiki/Impossible_Mission)
The code is totally rewritten, because it is easier to program the same functionality/narrative from scratch around my sprite engine, than to continuously reverse engineer the logic of the original byte code, and relocating functions from unusable memory areas. (I am already too old for that huge effort.)
Due to preserving acceptable framerate, my sprite routine uses lot of optimization which requires several changes in the game rules and narrative. I tried to find the balance between playability and similarity and sometimes this effort remain hidden. This makes the direct conversion also impossible. (For example the lightnings from the robots are shifted a few pixels down and dont't come out from the proper location of the robot head. That position is suitable for a 6*1 characters sprite, because it matches the character boundary. If I would have stick to the original placement of flashes, that would have required to use a 6*2 characters sprite, that notably would have affected the CPU cycles and the framerate.)
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