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using Manic Miner and Jet Set Willy game engines
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Message: 6909
Author: ian.rushforth
Date: 04/10/2016
Subject: Re: "Ma jolie" Game-engine bug / RZX walkthroughs
Danny wrote:
>(snip) "It's up to you whether you want to 'walk the plank' before
>or after you jump across the crumbling clouds, " (snip)
>
>In fact, you do NOT have to jump across the crumbling clouds from
>one end of the room to the other, and afterwards (or before) 'walk
>the plank'. You can get the rightmost item separately and afterwards
>(or before) jump across the crumbling clouds and drop down onto the
>ship, so that you 'walk the plank' only one way (saving some time).
>
>This involves using a quirky feature of the game engine which has to
>do with jumping off the top of the screen. I don't really understand
>how it works; I just know, by trial and error, that it does. I am
>pretty sure that it (or a similar, related feature) has been
>exploited (purposefully) in "Manic Scribbler" (in various rooms, I
>believe) and I have seen it happen (though not used purposefully) in
>the room "GoldenEye" (16) in "JSW64 Manic Miner: James Bond" (see
>messages # 6355, 6356 and 6357).
>
>Unfortunately, it also involves I believe the jumping-off-the-
>top-of-the-screen bug which tramples over memory when you fall off
>the bottom of the screen or jump up off the top, with the curious
>result that if you proceed this way in "Ma jolie" (either edition)
>the game becomes impassable later on, while in "Ma jolite" (either
>edition) you can still complete the game and (by saving time) boost
>your final score by over 100 pts.!
Firstly, I believe that the jumping off the top of the screen (causing corruption elsewhere) is a distinct phenomenon from walking sideways off the edge of the screen (causing Willy's sprite and his colour-attribute coordinates to become vertically detached).
Secondly, the corruption that can occur due to jumping off the top of the screen can vary, depending on how far above the top of the screen Willy's jump extends, and his frame of animation at the point at which he disappears off the top.
The attributes of the blocks that are written onto Cavern 7's layout data (and hence their behaviour when Willy interacts with them i.e. if they behave as Fire cells or not), depend on the exact value of the graphic bytes of Willy's sprite which are written to the errant addresses.
So without having investigated the exact circumstances you describe above, it is plausible that you might have caused non-lethal blocks to have appeared in "Ma jolie" (allowing the game to be completable), whilst conversely, the corruption in "Ma jolite" might have prevented the game from being completable - if only you had made the jump near the top of "The Mad Ramblings of Longbeard" from a different frame of animation at the start of the jump on each occasion!
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