Yars' Revenge-type game

[+atari2600land]

Hey, I'm fiddling around with an idea again, this time it's a thing like Yars' Revenge, and I was wondering what the Neutral Zone (the colorful thick line) in Yars' Revenge is made of and if I can duplicate it in bB.

[RevEng]

The Neutral Zone is made from one of the playfield registers, being fed varying parts of the program code as data.

 

It's not an easy effect to replicate with the standard bB kernels. I did one version of it in this thread, but it sacrifices a player to do it.

[+Random Terrain]

Related links:

 

http://www.atariage.com/forums/topic/170090-im-doing-it-wrong-but-it-works/page__view__findpost__p__2103953

 

http://www.atariage.com/forums/topic/121295-batari-wrote-an-example-of-yars-revenge-ion-field-awesome/

 

[Oops, I see one of the links was posted already. I started replying, then had to walk away and help watch a baby for a while.]

Edited January 6, 2011 by Random Terrain

[+atari2600land]

How would I make it different colors like in the game?

EDIT : OK, figured it out.

[RevEng]

here's v2 with per-line color, but you lose missile1 due to the multicolor player1.

 

It should also be noted that you can change the height of the effect with player1height, so you could create a zone that shrinks or moves around, or do something entirely different, like a transporter effect.

 

rem the energy barrier has large areas of blank space because this is a short program

set kernel_options player1colors

dim p1clo=player1color
dim p1chi=player1color+1

datastart
const datastarthi=(#>.datastart)

player1x=50
player1y=90
player1height=90
player1pointerhi=datastarthi
p1chi=datastarthi

gameloop
player1pointerlo=rand/2
p1clo=rand/2
rem COLUP0=rand
REFP1=rand
NUSIZ1=$07
drawscreen
goto gameloop

[+atari2600land]

I'm fiddling around with your code and I can't figure out why the qotile's missile isn't showing. (Don't be afraid, I've remarked the use of every variable.)

yar2.bas

[RevEng]

There were a few small things that were off... I commented the attached source code with my changes. The comments all start with "RevEng" to make it easier to find.

 

This is looking really good!

 

yar2.rev.bas

yar2.bas.bin

[+atari2600land]

Cool, thanks! I took your code and expanded on it even more, making this demo version (you can tell it's a demo because the colors change every 5 seconds like the early Atari 2600 games did when you first turn them on.) A surprising fact: when having player1colors on, putting "player1color=f" actually works for a one-pixel-tall sprite. I haven't checked this for sprites taller than this (which would be just about every sprite imaginable!)

 

yar2a.bas

yar2a.bas.bin

[RevEng]

It's impressive, especially for using the standard bB kernel!

[Piggles]

Cool, thanks! I took your code and expanded on it even more, making this demo version (you can tell it's a demo because the colors change every 5 seconds like the early Atari 2600 games did when you first turn them on.) A surprising fact: when having player1colors on, putting "player1color=f" actually works for a one-pixel-tall sprite. I haven't checked this for sprites taller than this (which would be just about every sprite imaginable!)

 

Well done! Go all the way good sir, and prove it can be done with bB!

[+atari2600land]

There's just one problem, though: The scanline count. It wavers somewhere between 261-263. This is evident when you look at the bottom of the screen and you can see it move back and forth one pixel, and you can also see the score move. Is there any way to fix this?

[RevEng]

I think it's a kernel bug.

 

If I use "const pfres=25" or "const prfres=23" (instead of the current "const pfres=24") then I get a steady 262 count.

Edited January 8, 2011 by RevEng

[+atari2600land]

Yes, but the score still wobbles. What is causing that?

[RevEng]

Yes, but the score still wobbles. What is causing that?

I see what you mean - I was testing on the earlier version, so I missed the wobbly score thing.

 

It looks like the kernel bug is still there... it appears to be triggered when you use no_blank_lines and pf_scroll.

 

Here's an unofficial fix. Stick the attached std_kernel in your yar build directory, remove the .txt extension, and rebuild your binary.

 

std_kernel.asm.txt

 

I can't guarantee that I haven't introduced some other bug with this, so don't replace your official kernel with it.

 

[edit - anyone wanting to see the change, just search for comments with "RevEng"]

Edited January 8, 2011 by RevEng

[+atari2600land]

Is there a way to get rid of the little line the same color as the playfield that shows up when the shield is at the bottom 3 positions?

[RevEng]

Its the "reboot" you're doing... the register that controls VBLANK is being zeroed before the background color is zeroed.

 

To hide the line you can do a "COLUBK=0" right before the reboot, though it would be much cleaner to not use the reboot at all.

[+atari2600land]

Here's a newer version. Next I will start working on starting the game and moving the ship.

yar3.bas.bin

yar3.bas

[lucifershalo]

Hurray for Yars 3

what is it going to be called?

Yar Strikes Back

Attack of The Yar

or the Phantom Yar ?

[+atari2600land]

How about "Yars' Other Revenge"? Actually, I don't know that much about the game, so I'll have to study the game some more in the near future. And "Yar 3" is just the name of the file, not the name of the game.

[+atari2600land]

To start the game, press fire. To fire the missile, press fire. Shooting the qotile doesn't work yet, and also the qotile doesn't spin and come at you yet.

yar4.bas.bin

yar4.bas

[+atari2600land]

Been slaving away at this for hours now since the last version. I've included a lot of things, including sfx. One thing I am having trouble with is thinking about how to display the Zorlon cannon. If anyone has any ideas, feel free to reply.

yar5.bas.bin

yar5.bas

[dbks]

Been slaving away at this for hours now since the last version. I've included a lot of things, including sfx. One thing I am having trouble with is thinking about how to display the Zorlon cannon. If anyone has any ideas, feel free to reply.

 

I looked at your code and you set kernel_options player1colors no_blank_lines so that means no missile0 && missile1 available, right? So you must use player1. I was just messing around and I came up with the following for using player1:

 

fire button - shoots the cannon

joystick - move yar guy

in the code set ZORLONMAXCOUNTER = 1 to draw it every frame or ZORLONMAXCOUNTER = n to draw it every n frames (this is so you can draw other things with player1 on the 'off' frames for the zorlon cannon).

 

zorlonCannonPlayerSprites.bas.bin

zorlonCannonPlayerSprites.bas

 

I also did version using the missiles, but I don't think it came out so good and you aren't using them any way, but here it is:

 

zorlonCannonMissiles.bas.bin

zorlonCannonMissiles.bas

 

My code might be messy and totally not what you're looking for, but I thought I'd show what I came up with.

[+atari2600land]

I guess the only way to show the Zorlon cannon is to have p1 flicker twice. I really didn't want to do this, but in the end, I don't know if it looks good or if it's a total flickerfest.

yar6.bas.bin

yar6.bas

[yuppicide]

Wow! That is fantastic!!!!!

 

You should make Yars Revenge 2.

[+Philsan]

Awesome!