Space Invaders Arcade

[NE146]

This looks great! I have yet to actually play it (working right now), but to me if it eventually supports the core SI arcade strategies that the typical ports usually ignore.. i.e. 1) counting shots and 2) 'wall of death' (or whatever you want to call it) where the invaders don't shoot on the bottom row, it'll be awesome enough for me even with 3 shields, especially on the 2600!   

 

[Thomas Jentzsch]

Shots counting is on my to-do list already. And the "wall of death" seems easy enough to implement too.

[CrazyChris]

Paddle support?

[Thomas Jentzsch]

27 minutes ago, CrazyChris said:

Paddle support?

Nope.

[+Karl G]

Paddles would make it a completely different game. 

[+fdr4prez]

Driving Controller support?

 

Trakball support?

 

Keypad support?

 

[Albert]

6 hours ago, Karl G said:

Paddles would make it a completely different game. 

Yeah, I agree, and if the goal is to make the game reasonably close to the arcade, paddle support would be going away from that.  Now, having said that, it would be amusing and kind of cool to play Space Invaders with paddle controllers, but it would make the game MUCH easier unless other changes were also made at the same time.

 

 ..Al

[Albert]

Thomas, this looks fantastic!  One thing I'd like to comment on is how the invaders move -- it seems like for each horizontal step they move more than they do in the arcade, which is a bit jarring since the rows look rather uneven as each row of invaders moves.  Is it possible to adjust this at all?  I'm impressed that they move down like in the arcade as well. 

 

I'm guessing there's no room or there's a technical reason why you can't use the "explosion" graphic for the invaders? 

 

Look forward to watching your progress on this!

 

 ..Al

[+sramirez2008]

6 hours ago, fdr4prez said:

Trakball support?

The 5200 version supports track-ball. I like playing it, but it does make the game easier.

[+Omegamatrix]

8 hours ago, fdr4prez said:

Driving Controller support?

 

Trakball support?

 

Keypad support?

 

Lightgun or nothing.

[+Karl G]

15 minutes ago, Omegamatrix said:

Lightgun or nothing.

That would be fitting if someone did a port of Space Invaders Frenzy, though. 

[Thomas Jentzsch]

12 hours ago, Albert said:

One thing I'd like to comment on is how the invaders move -- it seems like for each horizontal step they move more than they do in the arcade, which is a bit jarring since the rows look rather uneven as each row of invaders moves. 

Yes, the move steps are larger than in the arcade version. The latter moves 2 pixel per step (and has a higher resolution), mine moves in 3 pixel steps. This is a technical restriction. 3 pixel equal one cycle, which is the lowest possible resolution when using the RESP trick. Overall a step is about twice as large as in the arcade.

 

Also the arcade moves exactly one invader each frame. So it takes 55 frames for a full formation move. Since I cannot move single invaders (yet) I am trying to get close to this by moving each row individually (e.g. every 11th frame for a full row). 

 

12 hours ago, Albert said:

Is it possible to adjust this at all?  I'm impressed that they move down like in the arcade as well. 

The 3 pixel moves steps cannot be adjusted, but MAYBE I can find a way to move the invaders one by one.

 

12 hours ago, Albert said:

I'm guessing there's no room or there's a technical reason why you can't use the "explosion" graphic for the invaders? 

Yes. The invader sprites have to share the same graphics. And besides displaying the invader sprites, there is just enough time for displaying a missile. That's not enough for displaying a decent explosion.

[+johnnywc]

15 minutes ago, Thomas Jentzsch said:

Yes, the move steps are larger than in the arcade version. The latter moves 2 pixel per step (and has a higher resolution), mine moves in 3 pixel steps. This is a technical restriction. 3 pixel equal one cycle, which is the lowest possible resolution when using the RESP trick. Overall a step is about twice as large as in the arcade.

 I had the same issue in Galaga(on), however I am able to get a bit better movement by using 7 pixel sprites and using REFPx to simulate a 1 pixel move for one of the frames.  Galaxian achieves 1 pixel movement per frame by using 6 pixel sprites and using a combination of REFPx and the sprite graphics shifted right 1 bit.  For Galagon, they move 1,0,2 pixels per 3 frames since I went with 7 pixel sprites.

[Thomas Jentzsch]

1 minute ago, johnnywc said:

 I had the same issue in Galaga(on), however I am able to get a bit better movement by using 7 pixel sprites and using REFPx to simulate a 1 pixel move for one of the frames.  Galaxian achieves 1 pixel movement per frame by using 6 pixel sprites and using a combination of REFPx and the sprite graphics shifted right 1 bit.  For Galagon, they move 1,0,2 pixels per 3 frames since I went with 7 pixel sprites.

Yes, 7 pixel and 1, 2 steps would work. BUT IMO that doesn't look good for a game like SI, where initially you have a lot of sprites moving very slowly. Also the already quite wide spacing of the invader columns would increase even more. Even worse with just 6 pixel sprites.

[CrazyChris]

20 hours ago, Karl G said:

Paddles would make it a completely different game. 

I realized that after I posted... :)

[NE146]

Ok I gave it a shot and it's obviously very early, but looks great.. 3 shields and all!  Funny because I was able to get the regenerating invader, but I see that was mentioned already. The UFOs obviously also seem to come out a little too frequently for any shot counting to work correctly but again, just early stuff.  I like the movement of the invaders and the overall look. I was able to get a pseudo-"rainbow" bonus by shooting an entire column of invaders except the very bottom, so that's a good indication of the playability. I did notice the game had auto fire which the arcade of course doesn't have. It does make it more accessible though so that might be an ok thing to keep in. 

 

If it's worth anything.. I played a lot of Space Invaders. My high score in the game is in the 10's of thousands as when I was a kid I could play as long as I wanted (I think I could have probably gotten near the current world records if I had the endurance/motivation to do so). NOW on the other hand.. I'm not so sure.  But I'm still not too bad at it. And as such, I'm glad you're taking this on Thomas. Nearly all the classic Space Invaders ports missed the boat on what made the arcade game tick, or tried to inject a "new twist".  The SG-1000 I think was the 1st home port that I saw that had faithful elements to the arcade version, while still being it's own entity. But really that was about it until we started getting direct conversions like on the 16-bit consoles, or emulators.  So a VCS version with faithful elements but having it's own unique flavor would be pretty awesome to see.

[Thomas Jentzsch]

Thanks. I found some reference in the web which seems to be a good resource:

https://www.computerarcheology.com/Arcade/SpaceInvaders/

 

I man not sure if I can replicate all details, especially due to the technical restrictions. But the major elements will be there.

 

BTW: What's a "pseudo rainbow bonus"?

[Zoyx]

I was hoping it would be based on something like this ...

 

 

Good work so far, though.

 

 

Edited June 13, 2020 by Zoyx

[djmips]

7 hours ago, johnnywc said:

 I had the same issue in Galaga(on), however I am able to get a bit better movement...

Would your ideas run in 1977?

[+Karl G]

44 minutes ago, djmips said:

Would your ideas run in 1977?

Any of these ideas would have been possible, though they are advanced techniques that weren't known at the time. It's clever coding tricks rather than hardware assistance that makes it possible.

[+johnnywc]

1 hour ago, djmips said:

Would your ideas run in 1977?

Like Karl said, technically yes, although at the time I think they were just making 2K games so even a 4K Space Invaders would have been a stretch at least economically.  I'm not sure when the "RESP" trick was discovered or first used, but the Galagon kernels are direct descendants of the kernels used in Galaxian circa 1983.   

[NE146]

10 hours ago, Thomas Jentzsch said:

BTW: What's a "pseudo rainbow bonus"?

Sorry.. that was just a local term we used when you shoot a bottom invader last. The reason I mentioned it is sometimes it's hard to do in other ports of the game, making them feel not as faithful.

 

In the original it would trigger a bug where the invader leaves a trail, which we locally called the "rainbow" so I just always default to that name. ? The bug was pretty well known, so that in SI Part 2, they made it also trigger a 500-1000 pt bonus.

 

 

 

[Thomas Jentzsch]

Added V0.2 to the first post. Now you can shot at the shields and the saucer (direction and points defined by shot counts!).

 

BTW: I know there are still some collision issues at the bottom invader row.

[+Random Terrain]

Did the original arcade version let you hold down the button to keep firing or did you have to let go of the button and press again to fire?

[Thomas Jentzsch]

The latter. I changed that for V0.2, else you would have been able to kill the shields with rapid fire. Still have to add some "explosion" delay to the shots hitting the shields.