Re: [stella] Alpha version of my game

Subject: Re: [stella] Alpha version of my game
From: emooney@xxxxxxxxxxxxxxxx (Erik Mooney)
Date: Sat, 12 Apr 1997 05:50:19 GMT
>Let's see, that's 1978?  The same year Space Invaders came out.  (I'm
>26 by the way.  That's 1971, the same year Computer Space came out. 8)
>Seems like you'd be closer to the Nintendo generation than Atari, not
>that I'm complaining.  We need all the talented programmers we can

Just about everyone else my age considers the 2600 ancient history and the
NES the "cool" classic system.. they're Nintendo generation, but I'm firmly
Atari =)

>If you play more, you'll discover that not all bombs can be shot.
>Some just destroy your shots and keep coming!  I'm not sure if you
>should expand the invaders or not.  I guess you an give it a shot and
>see how it plays.

I rewrote the kernel to not reposition the ball (bombs), so it can only
handle one bomb at a time, or two on alternating frames.  The kernel now
barely fits within two scanlines within the invader block (if I don't WSYNC
at the end of the first line, I have enough cycles), and in about 1.1
scanlines outside.  I expanded the invaders to double-width and reduced the
player's missile to single-width, and the game does seem to play a lot
better now.

>> or on the same line as the shields.
>That could be aproblem.

Well, it's not a problem now, and it looks like I will have enough time to
write the player graphics registers four times for some decent-looking
shields.  Problem now is NUSIZ.. the easiest (only?) convenient way to do
four shields is two copies of each player.. but that "two copies" also
carries over to the missiles.  2600 Space Invaders seems to handle this by
using only one missile for player bullets in simultaneous mode, and drawing
those on alternating frames.. leaving the other NUSIZ register free to
generate 3 copies of its player for the shields.

Another possibility is three copies of player 0 and one copy of player 1,
drawing both missiles with missile 1 on alternating frames.. this seems to
be the only way to get a near-arcade representation of the shields.  Unless
I cook up some code that uses 3 copies of GRP0 when missile 0 is elsewhere
on the screen, and 3 copies of GRP1 instead when missile 1 is elsewhere on
the screen, and just pray that both missiles never end up in the same
vertical zone together with the shields =)

>I just saw three at a time in a quick replay, but it looks to be very
>rare.  Note that the bombs are not completely random.  The invaders
>tend to drop them in your area.

Three is rare enough in the arcade that I can get away with two, especially
because I'm not going to be able to display the little explosions when they
hit something, so I can recycle the bomb faster.

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