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using Manic Miner and Jet Set Willy game engines
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Message: 5796
Author: andrewbroad
Date: 13/04/2006
Subject: JSW pokes (Re: DrUnKeN mAsTeR!!!'s games - Daniel's review)
Daniel wrote:
>You must have the wrong number there. That POKE affects the code
> a) "The DrUnKeN mAsTeR!!!" original edition
>
> - There is an invisible item in "They smashed the stairs" (28). I
> guess this is a remnant from the original JSW. The item may be
> collected by jumping vertically up on the right side of the column
> after inserting e.g. POKE 35358,0.
which performs extra-life colour-cycling, which is unused in the
unpatched JSW game-engine:
{A contains the colour-attribute to be written}
35354: LD HL,#5C00 ; start of secondary attributes-buffer
35357: LD DE,#5C01
35360: LD BC,#1FF ;; 511 bytes to be copied
35363: LD (HL),A ;;; poke the first byte (top-left cell)
35364: LDIR ;;;;;;;; copy it to the rest of the cells
{Every cell in the secondary attributes-buffer now has that colour-
attribute}
The LDIR instruction behaves as follows:
1. copy the byte at the address in HL to the address in DE;
2. HL:= HL + 1;
3. DE:= DE + 1;
4. BC:= BC - 1;
5. if BC is not 0 then repeat Steps 1 to 5.
POKE 35358,0 changes one line of the above code as follows:
35357: LD DE,#5C00
So only the top-left cell gets set. Some cheat! ;-)
I think you mean POKE 36348,60, which lets Willy jump up through
Earth-cells on his left. This POKE alters the following code...
36343: LD A,(#80B2) ; Earth colour-attribute
36346: CP (HL) ;;;;;; compare with cell left above Willy's head
36347: JP Z,36540 ;;; if equal then go to 36540
36350: INC HL ;;;;;;;
36351: CP (HL) ;;;;;; compare with cell right above Willy's head
36352: JP Z,36540 ;;; if equal then go to 36540
...as follows:
36347: JP Z,36412 ;;; if equal then go to 36412
Likewise, POKE 36353,60 lets Willy jump up through Earth-cells on
his right. Both POKEs have nasty side-effects which can cause Willy
to become misaligned and fall through stand-onable cells until he
falls off the bottom of the screen.
--
Dr. Andrew Broad
http://geocities.com/andrewbroad/
http://geocities.com/andrewbroad/spectrum/
http://geocities.com/andrewbroad/spectrum/willy/
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