A simple scrolly bouncy demo

Anything Sinclair ZX Basic related; history, development, tips - differences between BASIC on the ZX80 and ZX81
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Shaun_B
Posts: 471
Joined: Wed Apr 22, 2009 10:22 am

A simple scrolly bouncy demo

Post by Shaun_B »

Here's a little BASIC demo that I wrote while messing about.

[EDIT] Version 1.1 is a bit better again I think.
[EDIT] Version 1.1a is further improved ;-)

Happy zXmas!

Thanks,

Shaun.
Attachments
ZXMAS_v1.1a.P
(1.96 KiB) Downloaded 119 times
ZXMAS_v1.1.P
(1.91 KiB) Downloaded 122 times
ZXMAS.P
A bouncy scrolly thingy
(1.54 KiB) Downloaded 123 times
Last edited by Shaun_B on Thu Dec 21, 2017 8:21 pm, edited 2 times in total.

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Paul
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Location: Germanys west end

Re: A simple scrolly bouncy demo

Post by Paul »

Thanks for the demo.
It works great in ZedEx on my android phone.
In theory, there is no difference between theory and practice. But, in practice, there is.

Shaun_B
Posts: 471
Joined: Wed Apr 22, 2009 10:22 am

Re: A simple scrolly bouncy demo

Post by Shaun_B »

Thanks Paul.

I'm going to see if I can make a reasonable snowfall-type effect with BASIC, but perhaps it is not possible.

Regards,

Shaun.

Shaun_B
Posts: 471
Joined: Wed Apr 22, 2009 10:22 am

Re: A simple scrolly bouncy demo

Post by Shaun_B »

I've made a slight improvement to the listing; in line 6, the cursor is re-positioned to the start of the line so that when line 3 fires (to clear the scrolly), it's already in the correct place. I think this makes for a slightly better frame rate as well. See below:
zx81-listing.png
zx81-listing.png (2.11 KiB) Viewed 2342 times
Regards,

Shaun.

Becky
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Joined: Tue Aug 25, 2015 9:41 pm

Re: A simple scrolly bouncy demo

Post by Becky »

That's really impressive. I would have thought it would be slower than that.

Becky.
2x ZX81 / 2xZ88 / Spectrum 48K / Spectrum+ / Spectrum +2 (Grey) / Spectrum +3
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sirmorris
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Joined: Thu May 08, 2008 5:45 pm

Re: A simple scrolly bouncy demo

Post by sirmorris »

I'm pleased that someone's giving the old BASIC ROM some lovin'! Keep it up Shaun :D

Is there some benefit to PRINTing AT 0+Y rather than just Y? There is a number parse and addition there that you don't have to do or so it seems to me.

Shaun_B
Posts: 471
Joined: Wed Apr 22, 2009 10:22 am

Re: A simple scrolly bouncy demo

Post by Shaun_B »

sirmorris wrote:
Thu Dec 21, 2017 4:37 pm
I'm pleased that someone's giving the old BASIC ROM some lovin'! Keep it up Shaun :D

Is there some benefit to PRINTing AT 0+Y rather than just Y? There is a number parse and addition there that you don't have to do or so it seems to me.
No, you're right, dumb mistake! It may be removed to save probably some processor t-states.

Regards,

Shaun

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