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Meteor Storm (Compute! Issue 29) - Fixed for XL/XE

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I've been messing around with magazine type-in games again these last few weeks, at the minute I'm on Compute!.


I came across Meteor Storm and couldn't get it working under XE OS. Tried all sorts but it wasn't happening. MC was the only way, but my MC-fu is weak. Several hours later and I've found a memory move routine that works backwards (necessary in this case). Several more hours later and I've got it working after figuring out how to do addition in MC (very painful). A couple more hours and I've integrated it into the game and it is working fine, to my eternal joy.


Fix notes:

This game refuses to work on XL/XE systems as originally printed. The reverse
scroll of the meteors is achieved by fooling the OS into thinking it is in mode
0 when it is actually in mode 1, and then printing an insert line character at
the top of the screen. While this works on the 400/800 OS, under the XL/XE it
does something evil to the display RAM, corrupting it and making the game

To fix this, I have added a small MC routine to replace the print of the insert
line character. The MC routine detects the address of the start of screen RAM,
and copies lines 23-3 to the next line down in reverse order. A normal memory
move wouldn't have worked as the source and destination overlap.


And here they are; bootable ATR (Basic required), and the BAS and LST (as a TXT) files for your pleasure. Enjoy!


PS, Atarimania are more than welcome to add this to their database as a fixed version.

Meteor Storm (XL fixed).atr



Edited by NuY
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Very cool. It's never too late to add a new universally compatible game to the 8-bit library. I was a Compute! subscriber for many years and sometimes typed in the listed programs. This is exactly the kind of obscure stuff I like !!! Thanks. :thumbsup:



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