Re: [stella] My game - Alpha 2 - inv.bin

Subject: Re: [stella] My game - Alpha 2 - inv.bin
From: emooney@xxxxxxxxxxxxxxxx (Erik Mooney)
Date: Sun, 13 Apr 1997 16:38:35 GMT
>Well, this time I got down to the point where the invaders land (at
>the beginning of the round(!)).  Don't forget to fix this in the final
>version.  I might also suggest some sort of pause between rounds.  I
>realize it's only an early version and you haven't had time to do
>everything yet, but I wanted to mention it.

I'll fix the limit on where the invaders start (sorry about that ;) ).  I'm
not sure if I want a pause between rounds, and it would be difficult to do
as-is (the draw-invaders kernel chokes if there's no invaders to display.)

>I found two bugs.  I'm surprised no one else commented on the first
>one.  As the invaders move, sometimes a gap between two columns will
>be have every other line in the color of the invader.  This occurs at
>the very beginning of each round, and also when they're about
>two-thirds to three-fourths gone.

Exactly when and where does that happen?  The number of invaders left
wouldn't affect it, but the location on screen (column) would.  I suspect
it happens somewhere on the left of the screen, which is where the invaders
are at the beginning of the round and when they're two-thirds to
three-fourths gone.  That sounds like a playfield register isn't getting
updated in time.  Is this on an emulator or on the real thing?

>The second one only happened once and I don't know how I did it.  I
>got down to one invader and it froze!  It was a green one.  It just
>stopped moving when I shot the second-to-last one, but kept dropping
>bombs.  I shot it and things resumed as normal.

That happened to me often during testing... I thought I had fixed it all =)
That happens when, for some reason, the game loses track of how many
invaders are left.  The count of "how many invaders are left", which is
used to set the speed of advancing, occasionally gets off by one or two.
That invader didn't quite freeze - it was just taking 255 frames between
advances, so it you had waited slightly over 4 seconds it would have moved.
I don't use that counter to detect when it's time to draw a new board - a
new board is initialized when all thirty playfield registers are empty.

Thinking about it now, that could still happen when both player missiles
hit the same invader on the same frame.. both players would get credit for
the kill, both missiles would be reset, and "how many invaders are left"
would be decreased by two.. but only one invader would be removed from the
formation.  Were you in two-player mode when this happened?

>Oh, and the auto-fire is good, but I think it may make things too
>easy.   (I might change my mind once the player can actually be
>killed.)  Maybe the difficulty switches should control this?

That's a good idea.. I probably will do that.  Unless someone can think of
a better way to use the difficulty switches.

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