[stella] Hello World

Subject: [stella] Hello World
From: "Roagie" <roagie@xxxxxxx>
Date: Sun, 7 Jul 2002 17:20:28 -0700
Hello all! I'm new to the list, but not to the cause. I've been collecting
for years and years and have finally gotten to the point where I want to
crack this 2600 nut.
My name is Brian, glad to meet you all!

I've made happy progress in analyzing how the 2600 does its business. This
started with Kirk Israel's excellent getting started page and his great
"thin redline" source code, which was commented for the extreme newbie, and
let me tell you it worked! Thanks Kirk! Using his source and the diagram on
page 2 of the SPG, it came all together for me last night at 1am. I am now
confident in my understanding of how to construct a kernel for a 2600 game
and handle the TIA and scanlines.

So now of course I want to actually draw something on the screen :)
So I check out "Crackers' Easy Playfield Graphics Code"
(http://www.neonghost.com/the-dig/source/crackers.asm) and start to check
out what's goin on there.

I follow everything fine except how the playfield gets loaded into memory.
1) When you define the playfield with a label, and then call the label with
a LDA, what *exactly* is loaded in to the accumulator when this single line
is executed?
This is the command:
LDA  playf0,X      ;load in the data for playfield 1
     STA  PF0

Also, what is X contributing to the process in the above LDA statement?

That'll do for now, any help appreciated. I'm also seeking any baby-step
docs similar to Kirk's redline demo... aka liberally commented source code
for newbies! :)

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