Date   : Tue, 03 May 2005 09:55:47 +0100
From   : Richard_Talbot-Watkins@...
Subject: Re: BBC B/Electron Chuckie Egg queries

Peter Edwards wrote:

> Hi,
>
> I have a couple of questions regarding the BBC B and Electron versions
> of Chuckie Egg, for accuracy's sake.
>
> 1)  What MODEs were the two versions written in?  I think it's BBC B -
> MODE 2, Electron - MODE 5 ... is that right?

Yeah that's right.  Funny this subject should come up, as, the other day, I
was trying to discover why the Mode 2 BBC Chuckie Egg is so lacking in
colour.  It looks like a Mode 5 game.  After some dissection, it turns out
that a lot of the palette is defined to be the same colour, so that when
sprites overprint, a dominant colour 'wins', e.g. the cyan birds - they are
plotted in colour 8, and then colours 8-15 are defined as cyan, so that
regardless of what colours appear when the bird is EORed with a ladder,
egg, or whatever, the entire bird still looks cyan.

Anyway, I decided this wasn't good enough :)

so with a bit of fiddling, here's an alternative loader which provides a
version as colourful as the Speccy version (white eggs and red background
on score, but without the yeuch colour clash):

=A0 =A010HIMEM=&3100 =00=A0 =A020*L.CH_EGG
3100 =00=A0 =A030?&4B7E=7:?&4CE6=32 =00=A0 =A040P%=&380:[OPT2 =00=A0
=A050LDA#&20:STA&FE6D:STA&FE6E =00=A0 =A060LDA#&22:STA&FE21:LDA&FC:RTI =00
=A0 =A070LDA#&26:STA&FE21 =00=A0 =A080LDA#&80:STA&FE68:LDA#&11:STA&FE69 =00
=A0 =A090LDA#&A0:STA&FE6E:RTS =00=A0
 100] =00=A0 110P%=&900:[OPT2 =00=A0 120SEI:LDA#&90:STA&220:LDA#&80:STA&2
06
:LDA#3:STA&221:STA&207:CLI =00=A0 130LDA#14:LDX#4:JSR&FFF4 =00=A0 140LDX#&2
7:LDY#0:.q
LDA&3100,Y:STA&110
0,Y:INY:BNEq:INCq+2:INCq+5:DEX:BNEq:JMP&
29AB =00=A0 150]
  160*TV0,1 =00=A0 170CALL&900

The main executable is assumed to be called CH_EGG and has the following
file info:

$.CH_EGG    001100  0029AB  002700

Thought I'd share that in case anyone was interested.

Happy Chuckieing!
Rich


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