Re: [stella] Gunfight 2600: The Final Kernel part 2

Subject: Re: [stella] Gunfight 2600: The Final Kernel part 2
From: Manuel Polik <cybergoth@xxxxxxxx>
Date: Wed, 16 May 2001 20:24:11 +0200
Hi Glenn!

> I noticed that the missiles kick up a scanline at the other end of the
> screen when you shoot them, sorta like what happens in Oystron.  Is this
> unavoidable?

Sorry for the delayed answer.

Generally it is avaoidable. The bullets are the only objects in
Gunfight, that can move everywhere, so all one'd have to do is doing the
CPX / PHP sequences during the horizontal blank.

The problem in the Gunfight kernel is, that I have lot's of other stuff
to do during these cycles. In the first line I need to very quickly
fetch, write & buffer the PF values, in the second line I've to do
player 0 very quick. Another point is, that you'd move the Stack to the
ball register, so you have to PHP the ball data first.

It just isn't possible to get everything timed perfectly - and least
hurting IMHO is doing the bullets on whatever place it fits without
causing any other trouble than a little shift.

Any other solution would force me to skip an other feature or to
horizontally reduce the field where the cowboys can move.

Displaying the bullets one line later than the playfield causes already
enough troubles BTW, as some bullets generally hit two blocks of the
obstacle. You'll notice that there's vertical positions where you can
fire straight through the coach and others where I need to constantly
alternate between two (block-) lines.


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