JetPac for the ZX81

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Bukster
Posts: 14
Joined: Wed Sep 12, 2018 9:44 am

JetPac for the ZX81

Post by Bukster » Sun Sep 16, 2018 4:23 am

Here's my first new game post on this forum, a ZX81 version of the Spectrum game Jetpac I finished earlier this year. It has four types of alien and two ships to assemble. This version features re-definable keys and variable difficulty levels which the original game didn't have, so the ZX81 is ahead of the spectrum on those counts.

I had to take some liberties with the game play and alien design to make it playable. The spectrum version had a laser that zipped across the screen. That would have made the game too easy, so this uses minus signs like bullets. The difficultly levels adjust the number of aliens and bullets from four aliens/eight bullets to eight aliens/two bullets. Extra life at 2000 points. The bottom line of the screen tells you what your current task is such as assemble of fuel your ship etc.

Give it a go and see what you think.
JetPac.p
(11.4 KiB) Downloaded 37 times
Attachments
Jetpac5.JPG
Jetpac3.JPG
Jetpac2.JPG

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zxooner
Posts: 30
Joined: Thu Aug 30, 2018 6:06 pm

Re: JetPac for the ZX81

Post by zxooner » Mon Sep 17, 2018 4:22 pm

@Bukster,

This looks awesome! Can't wait to try it out when the ZXPand+ arrives!

Thank you for sharing it 8-)
low res art for the Public Domain at the ArtBeSassy archive.

McKlaud
Posts: 176
Joined: Tue Dec 19, 2017 10:02 pm
Location: St Albans, UK

Re: JetPac for the ZX81

Post by McKlaud » Tue Sep 18, 2018 8:19 pm

Nice :)
Claudius
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Bukster
Posts: 14
Joined: Wed Sep 12, 2018 9:44 am

Re: JetPac for the ZX81

Post by Bukster » Thu Sep 20, 2018 9:57 am

I almost forgot, I have also produced an mp3 so you can play this on a real ZX81. I have loaded this and it does work. I always like my game to play on the original hardware. Here's a link to my webpage where you can get the mp3. I don't seem to be able to upload the mp3 to this forum, but you can get it from here.

http://bukstergames.bizhat.com/

There is a certain irony in using a 4.7Mb file to load 16k into a machine. Imagine if modern computers used every last drop of memory and processing power as efficiently as the early computers.

My site contains a few other minor ZX81 programs that I haven't posted here, at least not yet.

Fruitcake
Posts: 122
Joined: Wed Sep 01, 2010 10:53 pm
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Re: JetPac for the ZX81

Post by Fruitcake » Thu Sep 20, 2018 10:23 am

Jetpac looks great! Nice work.

Have you considered including Chroma colour support in the game? ;)

If you have a Window PC then you can use winTZX to create audio files from .p files as and when needed. The utility was improved last year to produce more accurate audio waveforms and also to include support for ZX80 files, and I've found it works remarkable well.

Bukster
Posts: 14
Joined: Wed Sep 12, 2018 9:44 am

Re: JetPac for the ZX81

Post by Bukster » Fri Sep 21, 2018 9:52 am

I've exchanged emails with Paul, the person behind the chroma interface. He was very helpful with technical details and my next game, a Berzerk clone will have chroma support. I'l consider revisiting Jetpac and adding colour if I can find the time.

Shaun_B
Posts: 421
Joined: Wed Apr 22, 2009 10:22 am

Re: JetPac for the ZX81

Post by Shaun_B » Mon Oct 15, 2018 8:22 pm

Got it running on my ZXMore - the speed increase / decrease helps for the 'turbo' mode @ 6.5Mhz.

This game is excellent. Thanks for your hard work. It's a shame I'm no longer a writer as this is definitely review-worthy.
JetPacZX81.jpg
Regards,

Shaun.

JohnsBargs
Posts: 18
Joined: Fri Oct 19, 2018 2:22 am

Re: JetPac for the ZX81

Post by JohnsBargs » Sun Oct 21, 2018 9:54 pm

Wee bug report, btw - if you get over 10,000 the score readout can't cope and clocks back to 0.

FrancoisLanciault
Posts: 20
Joined: Thu Jan 18, 2018 11:22 pm

Re: JetPac for the ZX81

Post by FrancoisLanciault » Tue Oct 23, 2018 4:45 pm

Does it have joystick support ?

Regards

Shaun_B
Posts: 421
Joined: Wed Apr 22, 2009 10:22 am

Re: JetPac for the ZX81

Post by Shaun_B » Tue Oct 23, 2018 10:45 pm

JohnsBargs wrote:
Sun Oct 21, 2018 9:54 pm
Wee bug report, btw - if you get over 10,000 the score readout can't cope and clocks back to 0.
At least you get a chance at another extra life then?

I only get one extra life at 2000 points and have not made the score 'wrap around' yet, so good work :-)

Regards,

Shaun.

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