> In the original Atari "Space Invaders" game: sometimes the invaders would
> explode when you hit them and sometimes they would just dissapear.
>
> I never found a pattern to it. Does anyone know why this happens?
Depends on whether the game needed the sprite to do something else, of
course :) Couldn't tell you exactly why and when, though.
> Note: I usually played by holding the "game start" switch down as I turn
> the game on, so I get two shots at a time rather than one. Maybe that
> has something to do with it?
That shouldn't have anything to do with the explosions. The only way the
one could affect the other would be if the code had difficulty handling
two explosions at once, which I don't think it does.
> By the way: Why does that "game start" trick work? Anyone ever look at
> the Space Invaders code to see why?
I'm fairly sure it's because the game number never gets initialized. On
powerup, the code sees the game start switch depressed, so it immediately
starts a game with whatever number happened to be in the "game variation"
variable, probably zero. For some reason, game zero allows shots for two
players, but only displays and responds to one joystick. (the invader
bombs and player missiles are drawn on alternating frames, all using the
ball - frame A repositions the ball halfway down to draw two invader
missiles, then frame B uses the ball twice to draw two player missiles.
Notice the bombs and missiles are not the same color as either player or
the invaders?)
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