Re: [stella] bipolar joustpong

Subject: Re: [stella] bipolar joustpong
From: Glenn Saunders <mos6507@xxxxxxxxxxx>
Date: Sat, 06 Sep 2003 17:01:29 -0700
Thinking on my feet here, if you use a regular playfield, rather than a symmetric playfield, you could use a single byte per playfield row and only use one half of the byte for each side. For PF0 on the left you don't have to mask anything because the register only uses the left 4 bits, but for PF2 you will need to mask the left half first and then store it.

Your playfield bitmap would therefore be only 4 bits wide on either side but you'd be able to have smaller blocks that aren't as tall because you are only using as many bytes as you want rows. 20 rows should be more than enough and yield somewhat square looking blocks. If you wanted more separation you can force a blank line between rows like Surround.

The logic to do this wouldn't take much CPU. You'd be indexing forward on a single zero-page address and taking care of both sides at once. You'd still have to blank out PF0 and PF2 so they don't repeat, of course. If you really started to run out of space you could interlace either side so that for any one line you will draw the left or the right half, but not both.

There should also be enough CPU time to do some color cycling also ala Warlords.

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