Resource centre for ZX Spectrum games
using Manic Miner and Jet Set Willy game engines
Archive of the
Manic Miner & Jet Set Willy Yahoo! Group
messages
|
|
|
|
|
Message: 6035
Author: Daniel
Date: 13/02/2007
Subject: Jet Set Emily FE - Bugfix release / Disappearing teleporter (!?)
I am pleased to announce the release of a bug-fixed edition of "Jet
Set Emily: Baby on the Go" FE (the game is by Steve Worek 2002-2005;
the modifications which led to the creation of the "Final Edition"
are my humble contribution). The only difference in the file as
compared to the initial December 2006 release is the starting point
(s) of the arrows(s) in the room "dark yet welcoming" (030), which
eliminates the nasty, infinite-death scenario (IDS) when entering the
room from the left, discovered by Andrew Broad.
Please download the ZIP with the bug-fixed file (and the "Jet Set
Emily - Final" text file updated accordingly) from the Files section
of the Group. The updated ZIP will hopefully also be coming soon to
JSE's homepage at http://xa.bi/jsw/emily.htm .
Since the only modification introduced is a purely "technical" one, I
have not given any descriptor to the new version of the game, hoping
that there will be no need for any further editions. However...
I have discovered a disquieting phenomenon during earlier playtests
of the game, and it happened again when I had another (rather
superficial) look at the bugfixed version yesterday. The problem is
that the teleporter sometimes disappears. Let me explain.
The teleportation module in "JSE FE" is located at the addresses
#81A8 - #81FF. It defines three teleporters: two leading
from "homestarrunner.com" (027) to "Shiggity Shiggity Shwa" (059) and
one leading back from that room to "homestarrunner.com". I created
the teleporters using John Elliott's teleporter extension and
following Andrew Broad's technical notes accompanying his "Jet Set
Willy: The Lord of the Rings". And it works fine, but sometimes
something bad seems to happen which makes the teleporter disappear,
or at least become dysfunctional.
When I compared snapshots of the game before and after it happened, I
found out that the problem is at the address #8B70, which has the
value "CD" when the teleporter works, and "01" after it has stopped
working. If I understand correctly, "CD" means that the teleportation
subroutine is called. So when this value is changed, it's no wonder
that the teleporter no longer works.
I think this is what happens, but I have NO IDEA WHY it happens. I
have not been able to associate it with any particular move or moment
in the game. I can only say - but without absolute certainty - that
it happened when I was playtesting the game in Spectaculator 6.1, and
it does not seem to have happened when using the ZX32 emulator (but
I'm not really sure whether the emulator has anything to do with it).
Can someone help me to explain this phenomenon and, most importantly,
explain what triggers it? And how can it be avoided?
Otherwise, there is a risk that there will be a random element to the
possibility of completing "JSE FE" successfully - much as Andrew
Broad assures us that the game engine is "a discrete
system which is 100% deterministic" and in which "there aren't even
any pseudorandom elements". I know Andrew is right, of course, but if
something happens and we don't know why, then we cannot avoid it, and
so for all practical purposes it IS a random event.
If the teleporter disappears before you have collected the two items
in "Shiggity Shiggity Shwa", you cannot complete the game
successfully. Unless it can reappear (can it?) or you POKE the game
engine to re-establish the correct value at #8B70.
And one more thing: when the teleporter has disappeared and you have
lost all your lives and restart the game, the teleporter is still
off. So you are doomed to failure from the very beginning.
Can anyone help with solving this puzzle?
Daniel
|
|
|