collision / division / inks

[egotrip]

I have a maze, with both deadly blocks and sprites. However, moving through it is impossible due to the super tight collision detection. Is there a way to loosen it up? I have tried the collision distance but that doesn't help.

Also is there any way to find out if a variable is divisible by a number, ie if x is divisible by 8? If not can you add that please?

Is it possible to change the colours of inks in the games? Palette switching would save a lot of RAM rather than having to use duplicate tiles in different colours, and being able to change the background on the fly would be useful too. (The help file does mention an INK command, but its doesn't seem to work, and seems to be copied into the help file from the speccy version)

[nra]

Hello Egotrip,

regarding DIV, try something as the manual says :
DIVIDE Y BY 8

As for detection, you're thinking right--try either alignment or a timer var (CLOCK) to make it more controllable. I wish Jonathan would add either sprite mask or vertical collision parameter, yet it's just a wish yet

[Jonathan Cauldwell]

Block collision detection is pretty tight and I can't think of a way to loosen it without rewriting that bit of the engine.

There's no palette switching I'm afraid, though it's something I may add one day. The COLOUR command is used to change the text ink colour, but that's all there is.

AS NRA says, you can use DIVIDE to see if a number is divisible by 8. So this code:

LET A = X
DIVIDE A BY 8
MULTIPLY A BY 8
IF A = X
..
ENDIF

should do the job.

[egotrip]

thanks for the replies

[egotrip]

DIVIDE does not work in the CPC version - are you sure it is included? It's not even in the manual.

[Jonathan Cauldwell]

You could be right. I'll add it to the to-do list.

There should be another way to check if a number is divisible by 8. Try this:

LET A = X
MULTIPLY A BY 32
IF A = 0
(number is divisible by 8)
ENDIF

...and see if that does the trick.

Thinking about palette switching, you can do it with the ASM command if you really want - but be careful. The way to do it is like this:

ASM 62
ASM p
ASM 1
ASM c
ASM c
ASM 205
ASM 50
ASM 188

where p is the palette entry (0-15) and c is the colour number.

[egotrip]

That multiply trick seems to work. Thanks.

However it doesn't help me, because I need it to check if its divisible by 2 or 4, not 8.

[Jonathan Cauldwell]

To check if a number is divisible by 4, multiply by 64. For 2, multiply by 128.