BTW: I don't think a screensaver mode is necessary any more. And it "wastes"
a lot of valuable space.
<<
If the game has the space left over, it goes a long way to adding that
little extra bit of retro authenticity. It also performs a utilitarian
function, namely visually indicating when the game is over. Space Invaders
a good example of that. I like the way the game kinda still runs in that
game even though the game is over. It's like an "afterlife" mode.
GLENN SAUNDERS===============================
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From: "Thomas Jentzsch" <tjentzsch@xxxxxx>
Reply-To: stella@xxxxxxxxxxx
To: stella@xxxxxxxxxxx
Subject: Re: [stella] Help (Timing problems?)
Date: Tue, 31 Jul 2001 09:23:55 +0200
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Wade Brown wrote:
> I am working on a "shell" that I can use to flesh out some ideas I have
-
> the idea being to have basic semi-reusable functions such as: b/w color
> selection, screen saver timer, and score digits.
That's a good idea, if you want to start programming the 2600. Later on,
you will find, that often you need more specialized or optimized code.
> BTW, I was trying to get a fairly optimal way to read diagonals from the
> joystick - anyone out there see how I can improve this approach or has a
> different take, I would really like to see...
The code below is a bit more compact than yours:
; check joystick:
lda SWCHA
asl
bcc .noRight
inc Player1X
bcs .withJoy ;3 always taken branch, saves 1 byte compared to
jmp
.noRight:
asl
bcc .noLeft
inc Player1X
bcs .withJoy ;3 always taken branch, saves 1 byte compared to
jmp
.noLeft:
asl
bcc .noDown
...
bcs .withJoy ;3 always taken branch, saves 1 byte compared to
jmp
.noDown:
asl
bcc .noJoy
...
.withJoy:
ldy #0 ; joystick moved
sty SaverTimer
.noJoy:
> I would especially appreciate any help in the
> area of boundary detection (i.e detecting when the player/enemy is at
the
> edge of the screen).
Here is a slightly better solution:
; check x-bounds:
; I LOVE to use constants, because that makes the code more readable (for
me:) and I can much easier change the parameters
LEFT_BOUND = 20
RIGHT_BOUND = 140
lda Player1X
cmp #LEFT_BOUND
bcc .outOfLeftBound
cmp #RIGHT_BOUND+1
bcc .inXBounds
lda #RIGHT_BOUND
.byte $2c ; opcode for bit.w, this hides the next
instruction
.outOfLeftBound:
lda #LEFT_BOUND
sta Player1X
.inXBounds:
You could also combine the joystick and boundary routines. This might give
you more optimal solutions. But that's mixing two different basic functions
and doesn't fit into your concept.
Have fun!
Thomas
BTW: I don't think a screensaver mode is necessary any more. And it
"wastes" a lot of valuable space.
_______________________________________________________
Thomas Jentzsch | *** Every bit is sacred ! ***
tjentzsch at web dot de |
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