;-------------
; Shadebobs
;-------------

In "Unreal", "Amnesia", "Delusion" and others there is a sort of shadebob
technique that is used. This technique is pretty simple, any demo maker
knows much slicker routines than this one, but this will give everyone else
some ideas on how it's done.

What you do is move a set of X and Y coordinates around as you please. These
represent the upper left corner of the bob. Then, you call a subroutine to
draw the bob. The easiest way to explain this is a BASIC code chunk.

DEF SEG = &HA000
FOR BX = X TO X+SHADEBOBSIZE
  FOR BY = Y TO Y+SHADEBOBSIZE
    POKE (Y*320+X),PEEK(Y*320+X)+4
  NEXT BY
NEXT BX

This is obviously going to be VERY slow... but with a little work, you can
crank it out in ASM and even this algorithm (which is the one I used) can move
at a decent speed.