demo_07_sprites4.txt

******************************
*        AGON LIGHT 2        *
*          DEMO 07           *
*      BBC BASIC MODE 8      *
*       SPRITES PART 4       *
*      THANKS MILTON W       *
*       BY LOVEJOY777        *
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The -1 is because you loop from 0 (line 2540).
If you want to loop through 3 elements (r,g,b) you could do 'FOR %I=1 TO 3'
but then you would need to subtract 1 (times 3) from the memory lookup (e.g. ?(graphics+I%+0 - 3).


The alpha is calculated as a bitwise OR.
Lets say r% = 1, and g% = 2, then r% OR g% is 3.
It's not the same as r% + g%!
If r% is 255 then any OR will be 255. since all its bits are already '1'.
Meaning any colour other than 000,000,000 (black=0) will be 255 (either on or off).


The 'VDU r%, ...' (line 2590) is still in VDU 23,27,1,W%,H%,... (line 2530)
It expects the WH4 bytes to follow.

'VDU' is just a synonym for PRINT (or printf if you will). So VDU 23 just sends a 23 to the VDP, and VDU r% sends r% to the VDP.