TROGBlog

Next time use

...

please.

For a variable-height ball (or missile), maybe use this code:

   lda BallHeight
  dcp BallTemp
  sbc BallAdjuster
  sta ENABL          ;+14

Where:

BallTemp = Height of screen - Top line of ball

BallAdjuster = BallTemp - 2

 

There are a lot of possible variations there...

if BallHeight is fixed:

   lda #BALLHEIGHT
  dcp BallTemp
  sbc #BALLHEIGHT-2
  sta ENABL       ;+12

If BallHeight is variable, but you can restrict it to...umm, let's see if I can remember how this works...if you can restrict it to the form C + 4x, where C is a constant, then you can use this code:

   lda BallHeight
  dcp BallTemp
  sbc #BALLADJUSTER
  sta ENABL     ;+13

Where BALLADJUSTER = the constant C plus 2.

That gives you 4 options:

Ball height could be 1, 5, 9, 13, etc. BALLADJUSTER would be 3.

Ball height could be 2, 6, 10, 14, etc. BALLADJUSTER would be 4 (or zero).

Ball height could be 3, 7, 11, 15, etc. BALLADJUSTER would be 1.

Ball height could be 4, 8, 12, 16, etc. BALLADJUSTER would be 2.

 

If I remember correctly, though, the actual displayed height of the ball will be BallHeight - 1. So for a ball a single scanline high, use a height of zero.

This is coming along very nicely!

 

A suggestion - would it make the game look more "Star Castley" to color cycle the shields between yellow and red?

 

Like so:

 

 

Although I suppose to really mimic the original... space would need that "blue overlay" look:

 

 

Hmmm. Nah. Black looks better.

Next time use

...

please.

 

Thomas, I'm still kinda noobish with the forum interface, so I'm not sure what you mean here. I used the code tags. Is there a way to make the code section collapsable/expandable?

 

vdbu_bobby, thanks for the suggestions. I tend to avoid illegal opcodes unless I really need the cycles. Currently the kernel does everything I need it to, so I don't plan to cram anything more in unless there's a way I can shave off a ton of cycles (a ton being 5 or more.)

 

Nathan, nice suggestion. I may take you up on that. Keep in mind that I'm not trying to do an exact port of the game, for copyright reasons. This literally is "an artistic reinterpretation." I already have some plans to deviate from the original game. Specifically, a slight retooling of the kernel will allow me to add enemy attack ships in the upper and lower empty space of the screen. These ships will show up occasionally on harder levels, similar to the random ships in asteroids.

 

I may also make a "classic" option in the game, which will match the original game as closely as possible, and then all the other options will have my own added features like the enemy ships, variations in the number of interceptor missles, different shield ring configurations, etc. Also, on harder levels, the rings will slowly regenerate, differing from the full regeneration if a ring is totally destroyed.

Thomas, I'm still kinda noobish with the forum interface, so I'm not sure what you mean here.  I used the code tags.

My problem is, that the formatting got completely lost, making it hard to read the code. AFAIK you need to replace any tabs with spaces before posting and you have to add an extra space when indenting.