Talk:Space Invaders

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Contents 1 Accuracy 2 Update Speed 3 More on the speed up issue 4 Original Programmer 5 It was so popular because... 6 Different game w/ same title? 7 The dance 8 Is Space Invaders Japan's first video game? 9 Atari 2600 Version

[edit] Accuracy

I question the accuracy of the paragraph:

the remaining aliens would move faster and faster...

If the computer was just updating the screen more often, the shot and player's base would move faster as well, but they didn't. They moved at the same speed throughout the level's progression. So some elegant programming had to be involved in the implementation of this feature. Anyone else? —Frecklefoot 19:31, 11 Aug 2003 (UTC)

It's surely true that there was some clever programming going on, but I'm not clear as to what exactly you are questioning. Nobody seems to be claiming that a particular programming technique was used; in any event it's absolutely true that the remaining aliens moved faster. What's to question? Jgm 00:58, 10 Aug 2004 (UTC)

"The player's cannon could be destroyed three times (the player had six lives), and the game would end after the player's last life was lost." - This can't be right, can it? By my definition of "lives", the player had three. However, I'm not sure what the best way is to re-write the sentence, since the sentence structure itself isn't how I would write Jfiling 15:27, 21 December 2005 (UTC)

[edit] Update Speed

I have to agree with the previous poster. I once had a job programming video games in the early 80s, and although the processors were pretty pathetic, the situation regarding update speed is more complex than that the main update loop is speeding up simply because it has fewer entities to update. Trying to update a full screen of aliens at the speed of the last alien would probably choke the processor, but as the previous poster has noted, only the final alien is moving faster at the end of a round; the shots, the saucers, and the player's ship are all moving at the same speed. Only a careful inspection of the code could determine exactly how the speedup is accomplished, but in my shop, it was standard practice to implement an round-robin master routine, which would poll the controls, tick the game model, update the display, and then sleep for a few milliseconds.

• That paragraph seemed bad to me too... I'd like to see some sources before allowing it in the article. --Yoshi348 17:13, May 19, 2005 (UTC)

Not sure why you'd write a polling routing for controls and video display when the 8080 CPU, or any of the CPU's of the late 70's in a standard bus/memory configuration were perfectly capable of handling up to 8 interrupts with 8 bits of data per interrupt on the hardware bus. The display in space invaders is totally independant of the mother board - it has a completely separate daughter board with its own video memory. There is not enough going on in Space Invaders to choke the CPU - even at 2khz. The sound is totally discrete, the video has its own CPU and memory, the only thing the mother board has to do is coordinate and move/copy memory. While Gorf, for example, runs at 1.7KHZ, this is slower with a lot more going on, and Gorf does not choke at all, even using 4bits / pixel.

[edit] More on the speed up issue

Also, when there is only one alien on the screen, the alien moves at a different speed going to the left, than it does going to the right, and the player's ship moves the same during this whole time.

I have reinstated text to the effect that the alien speedup is a result of there being fewer aliens to draw. It is not true to claim that everything else would speed up if this were the case. Space Invaders does not update every alien every frame. It doesn't have any hardware help with sprite drawing and the CPU simply isn't fast enough to move that much data. It wouldn't be surprising if it updated exactly one alien per frame. When there are fewer aliens, the turn of the remaining aliens to be moved comes up sooner.

As an example, consider the case when there are 30 aliens on screen. In frame 1 the first alien is moved. In frame 2 the second alien is moved, and so on. After the 30th frame, the game returns to alien 1. Therefore, each alien is moved once every 30 frames.

Now, imagine 15 of the aliens have been killed. Now each alien is moved once every 15 frames. Since the amount they move is the same, the aliens are now moving at twice the speed without any change in UFO or laser cannon speed.

This also explains why the speed difference is most pronounced when moving from two aliens to one. The time the remaining waits for is reduced by 1/2 - i.e. he starts to move at double the speed. Conversely the move from 30 to 29 aliens is only a reduction in the time each enemy sits before moving of 1/30th.

This can be verified by playing the game and watching the way in which the aliens update or, if necessary, the original game source. The 8080 is a very simple processor and the code is quite easy to follow.

P.s. I wrote the above a day or so ago, but neglected to sign it ThomasHarte 00:19, 6 August 2005 (UTC)

I agree with the above, and have always assumed this was the case. In fact, I thought you could visibly distinguish that only one enemy updated per frame, which you can see as a 'wave' moving through the formation. Can anyone verify this with an original machine or emulator? JasonAD 04:38, 5 June 2006 (UTC)

[edit] Original Programmer

I removed the following bit from the article

...and programmed by California teenager David Yuh

Google searching for David Yuh show us a surgeon, not a programmer. But searching for "David Yuh" "Space Invaders" give us 3 results, and one of them indeed has an anedoctal account of a 16 years old teenager, now a succesful surgeon that coded the original Space Invaders.

Although I think this story is perfectly plausible, I would like to have some more sources sited for this information. Regards, --Abu Badali 15:41, August 4, 2005 (UTC)

[edit] It was so popular because...

I was a teen when this game came out. I had been playing all kinds of arcade games before Space Invaders appeared, and there was one feature above all others that made this game so much more popular than all of it's predecessors. That is, if you were any good, you could play for much longer than the other machines for no extra money. On earlier arcade machines, the play time was time based. That is, there was a clock, and once your time was up the game was over. Maybe you could earn some bonus time, but once that expired it was game over. Space Invaders changed all that. In this game you had three "lives", and the game only ended when you got killed with noi more lives left, not when the clock struck 12. This has never been mentioned in other Space Invader discussions anywhere that I have seen, but this was definitely the big plus in this new game. I'd like to see this added to the article. --Commking September 8, 2005

It sounds plausable. But if we had a source that would be better. --JiFish(Talk/Contrib) 00:03, September 8, 2005 (UTC)

All I can say is, I was there. What better source can you get? This was the first video game I/we saw that allowed you to play longer according to your skill level, instead of according to the clock. I welcome anyone who can say there was a video game that had this feature earlier. --Commking September 9, 2005

It might be considered original research. But if I was you I'd be bold, add it and see what happens. --JiFish(Talk/Contrib) 17:29, September 9, 2005 (UTC)

OK, it's done. Last paragraph under "popular response". I am not much of a writer, so feel free to reword it if needed. --Commking September 13, 2005

[edit] Different game w/ same title?

I once had a game for my Mac that was called space invaders but looked nothing like these games. I had it back around, 1997(?). Here's a description and if anyone knows what I'm talking about and doesn't think I'm crazy, please tell me where I can find this game and/or more information about it: You start off as a little cannon that moves back and forth across the screen. The only ships that you can shoot are these little ones that change colors each time you shoot them until finally they go away. There are much bigger and more powerful ships that come and go, but you can only shoot those if you have the laser upgrade. Until then, however, you can shoot the bombs that they drop. Does anyone have any idea what I'm talking about?

[edit] The dance

One of the more surreal experiences in a gaming history exhibition I attended circa 2003 was seeing a video of the Space Invaders craze in Japan, which included a dance floor full of Japanese people in neatly lined rows moving rhytmically sideways. Mentioning this might be neat, but I haven't been able to source. --Kizor 11:23, 31 July 2006 (UTC)

[edit] Is Space Invaders Japan's first video game?

I've been reading a bit of video game history and if I'd like to confirm if Space invaders was Japan's first ever video game? Because if it is, it might be worth mentioning in the article.

• No. Taito first started with a a number of video games in 1973, including Astro Race,Davis Cup,Elepong,Pro Hockey, and Pro Soccer.They continued manufacturing games all through the 70's. Probably their best known "pre-Space Invaders" game was 1975's Western Gun, which was released as Gun Fight in the U.S. by Midway Mfg. Co. --Marty Goldberg 19:25, 12 October 2006 (UTC)

[edit] Atari 2600 Version

I disagree with the statement about the Atari 2600 version, "Not only did it capture the feel (if not the exact look or sound) of the original arcade version..."

Although you may argue that it's a subjective analysis, none of those statements are true.

The "feel" -- there was a slight delay in firing in the arcade version. The Atari 2600 version fired almost immediately, without the pause at the beginning and end of the shot.

Look -- not even close. Some of the invaders looked similar, but some were completetly different and had different motion.

Sound -- again, not close. The firing sound in the arcade version sounded more like a laser. The Atari 2600 version sounded like a pop gun.