Re: [stella] Thrust!

Subject: Re: [stella] Thrust!
From: Thomas Jentzsch <tjentzsch@xxxxxxxx>
Date: Fri, 19 Nov 1999 12:53:27 +0100 (CET)
--- kurt.woloch@xxxxxxxxx wrote:

> Hmmm, the Kernal (and thus, the timing issues) is
> another problem, but as I
> see it, M2 is still free. Maybe you could do some
> kind of that trick as used
> in Missile Command for the missiles, and Decathlon
> for the pole, in Pitfall
> for the ropes etc. where a missile is displayed
> which gradually changes
> position with HMOVE's on every, or every other,
> line. As long as the crystal
> ball is well under, or over, the ship, this should
> work, as well as
> displaying the ship and the ball with the same
> player in one frame. 
This sounds good, still i have to find the time for
Here are some explanations/limitations of my
- the kernel is repeated every 4th line
- the players and missiles are changed every 2nd line
- all missiles are only 2 lines high
- one new PF-block _or_ a multi-used-player can start
every 4th line

Drawing the missiles is very simple now:
    ldx #ENABL    ;2
    txs                 ;2
    cpy BLline      ;3      
    php                ;3      got this trick from
    cpy M1line      ;3
    php                ;3
    txs                 ;2      
    cpy BLline     ;3
    php               ;3
    cpy M1line     ;3
    php               ;3 

This makes just 24 clocks for 4 lines. 
To draw a higher missile, i need totally different
which would cost some extra time, which i haven't
yet. (about 2*15 clocks for the compares an stores,
the 9 clocks for two HMOVEs and one HMCLR to 
prevent the players from moving arround (there is no 
HMCLR in my kernel now), plus at least 5+3(*2?) 
clocks for loading and storing the values for HMM0, 
this makes ~50 clocks) 
Drawing the fire- and the wire-missiles on different 
frames, would add some more flicker to missile fire. 
I have to find out, what is possible and looks best...

> If the
> ball gets to near vertically, you could switch to
> another mode where the
> ball is displayed alternating with the ship
> (flickering), and also another
> solution's used for the wire.
I don't want the ship to flicker, because this is the 
point where the human player is most focussed at. 
So i'll better let some of the other players flicker.

> Sorry, I can't figure out what this means... could
> you further explain how
> you store the terrain data?
I'll try: looking at the smallest level 1 (red PF) you

can divide it into three parts: sky, cave and socket.

For the sky and the socket i need one block each for 
the two sides of the PF, which makes a total of 4
blocks. The cave consists out of two blocks for both 

(use fixed-font for the following "graphics"!)
left border blocks             right border blocks
    /                                        \
sky-|                                        |-sky
    \                                        /
    / ----                        P     ---- \_bl1  
bl1-| ------                          ------ /
    \ --------   F              ------------ \
    / --------------            ------------ |_bl2
bl2-| ----------------G         ------------ |
    \ ------------------        ------------ /
    / -------------------------------------- \
soc-| -------------------------------------- |-soc
ket \ -------------------------------------- / ket

Level 4, which is were the demo starts, has
15(cave)+2(sky, socket) blocks for the left, but 
only 6+2 blocks for the right border.

> How many "blocks", roughly, are used for each level?
There are between 4 and ~20 blocks used for each 
(4..~20) * 2[both borders] * 4[bytes/block] 
 = 32..~160 bytes/level

> So
> maybe it'll be better to relocate those fuel
> stations to other places in the
> level, or simply put one fuel station there which
> has got a bigger capacity
> instead of the multiple ones...
That's exactly what how i planned it.

> Ah. I didn't try that... I thought the fire button
> was totally inactive...
> has it got other functions too?
No, it just fires the missiles, and the gate-opening 
function is only temporary.

Thomas Jentzsch           | *** Every bit is sacred ! ***
tjentzsch at yahoo dot de |
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