[stella] best practices

Subject: [stella] best practices
From: Glenn Saunders <cybpunks@xxxxxxxxxxxx>
Date: Mon, 08 Jan 2001 22:11:21 -0800
At 12:28 AM 1/9/2001 -0500, you wrote:
You could switch the every-other-scanline and every-8-scanline sections
depending on when you need to draw what.  In that case you would need to
hang a label on the every-other-line section and BNE to that rather than
EndOfLine.  I'm sure there's a more efficient way to do this, but this is
the obvious way to me.  (Well, except I'd do it as a DEC loop rather than
an INC/CMP loop, as you imagined, cutting like 5 cycles out of the 68 or
however many you have to spend on a line.)

I can do the bottoms up thing, but it just makes some things more confusing.

The screen is scanning from the top down and the graphics are spooling from the rear end upward. What will be especially difficult is taking a sprite collision and translating the fine/coarse positions into a playfield write to generate the tombstone. It looks like tables will be easier than calculating it.

But after 20 years, there are certainly a heep of 2600 best practices for programmers, and with this sort of kernel I don't think I can afford taking the sloppy route. Ram is going to be especially tight, for instance. The main playfield bitmap will consume 96 bytes all by itself!

It really is fun, though, hearing all the different ways to accomplish the simple goals with assembly. It's very refreshing compared to how I'm used to writing things in Basic, Javascript, and CFML.

BTW, I was thinking about having a paddle option for this game, but I don't think it's going to be possible because of the timings of having to discharge the pots during screentime. The dual need for a playfield bitmap and adjusting the width and position of the missiles on the scanline isn't going to leave much time to read the paddles, although I could maybe make the missiles 7 scanlines tall and reserve the last line for the paddle read.

But using the driving controllers seems like it will yield an easier kernel.

Glenn Saunders - Producer - Cyberpunks Entertainment Personal homepage: http://www.geocities.com/Hollywood/1698 Cyberpunks Entertainment: http://cyberpunks.uni.cc

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