Re: [stella] invaders idea

Subject: Re: [stella] invaders idea
From: Glenn Saunders <krishna@xxxxxxxxxxxx>
Date: Sat, 12 Apr 1997 19:40:18 -0700 (PDT)

On Sun, 13 Apr 1997, Erik Mooney wrote:
> both missiles and the ball using the PHP trick, writes the playfield
> registers 12 times, increments a scanline counter, and decrements a

I don't know exactly how you are drawing the playfield, but you are
working with the Starpath environment so you do have RAM and more space to
work with.  It seems that you could store two copies of invader shape data
(FRAME 1 and FRAME 2) and just substitute it at the necessary rate like a 

> This will be more difficult, because I don't have the time to do anything
> besides loading and storing the playfield graphics on the same scanline
> pair on which I check the missiles and the ball.  I'll try with the first

There may be a better way of implementing playfield graphics when working
in the Starpath environment.  You may be able to simply manipulate
everything at the bitmap level (writing to Starpath RAM) and refresh the
playfield registers at regular intervals so that you don't have to play
any of the normal CPU-intensive playfield manipulation tricks.  If doing
it this way is a lot less CPU-intensive then maybe you'd free up enough
cycles to color-stripe the playfield more radically.

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