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Some progress on Space Invaders 7800

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PacManPlus

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Finally got to work on this a little this past week, and I made a little progress, and ran into some stumbling blocks. There are some screenshots below :) As of right now, my biggest issues with this are:

 

1) How to do the shields, and have them 'break away' piece by piece. I am assuming they have to be sprites(like the ufo and player) instead of cells from a character set (like the invaders), but I haven't a clue how to start it.

 

2) The left and right edges. Being that the screen is being manipulated to give the illusion of the invaders 'marching', I'm wondering how I'm going to know when a left-most or right-most column of invaders are completely cleared. I need to know this because any time an outermost column is cleared, the remaining invaders now march to that edge. So the edge boundaries need to be moved, in effect. hmmm.... Keep an 11 member array of the invaders, (think of the invaders on their side), and when the first or last members equal zero I'll know an entire column has been destroyed... maybe...

 

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04/14/08:

blogentry-1787-1208225785_thumb.png

 

06/13/08:

blogentry-1787-1213364189_thumb.png

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Does the code you wrote assume all 16 rows of RAM are each contiguous page?

 

My code pretty much requires the memory layout my DLI code provides, since it expects rows to be equally spaced in RAM. For optimal performance, the row spacing times the explosion height should be 255 or less.

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Thanks Supercat - I guess I misread the code then.

 

Please don't be annoyed with me, but I just don't understand the DLI code that you wrote there. :)

This is the part that actually scares me; when I don't understand something I think I should, I truly feel like I'm becoming more stupid as I get older. *Especially since I am a programmer by trade* (although we use C, C++ and C#)

 

If I'm struggling with a simple game like Space Invaders, I can forget about doing anything more complicated :-/

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Ok, some good news now. I enabled 'Dual Player Mode' and the screen didn't jump with both players on the screen (shooting), both invader shots, the invaders, and the ufo!

I wish there was some way to tell how many cycles I have left before I start getting screen jumps / slowdowns.

 

Now I start to work on sound. Then 'attract mode'. Then player options.

 

Bob

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If I'm struggling with a simple game like Space Invaders, I can forget about doing anything more complicated :-/

Don't feel bad - the DLI code he posted is fairly complicated IMO. :)

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Thanks, Bob, and thank you Supercat

 

Ok - my beginning of working with sound for this game led me to a discovery: the invader's "march" sound isn't in time with the movement! Only the first few invader hits keep the same time, then they start to separate. This gap increases as more invaders are cleared from the screen. I always thought they were exactly the same. :-/

 

It's not that noticable in the arcade because of the 'delay' (the arcade actually moves one invader per frame). It is noticable here, but I think it's ok.

 

Update in first post.

 

(still, so far so good with the CPU cycles) :)

 

Bob

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More sounds added (Player death, Shot, Invader hit) - update in first post

 

... although there's one thing which puzzles me: It seems like the sounds are a frame behind the animation, no matter where I put the call to the sound subroutine in the main loop :) Does anyone know what that may be?

 

Bob

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Thanks Walter :)

 

BTW - Nevermind about the sound issue. When I try it on the real thing, there's no delay.

I've added the UFO sound, and the UFO death sound. Just need to add the 'bonus ship' sound.

 

No update bin yet, as I want to start on the attract mode and selection screen.

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Hi Bob

I saw another original Space Invaders.Its name is "Time Attack" and it is for the Nuon.Would be great to see this Invaders too.Would it be possible to make a Multicart,like you did with PAC MAN?

greetings Walter

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Hey Walter:

 

I'll see if I can find some screen shots and take a look at it. :) I'm adding as many options from the 2600 version as possible, so hopefully it won't get dull quick. :D

 

I kind of wanted to keep this one at 16K, but I'll what I've got once I'm finished (I know it's a 32K bin at the moment, but I'm going to reduce it).

 

BTW, I am now about 3/4 done with what I set out to do, so I am now moving this to the 'Homebrew' forum and starting a thread there.

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