' I think this program implements Brownian Motion.
' Or something like it, anyway.
' Allan Crossman, 2001

' OPTIONS YOU CAN FIDDLE WITH:

colonies = 5      ' More is slower.
store = 1000      ' More means bigger colonies.
jumpsize = 0.5    ' More than 0.5 leaves gaps in coverage.

width = screen width
depth = screen height - 20

y_offset = 20     ' This just moves the whole window down this much
                  ' I use it to accomodate the menu bar.

overdrawprob = 0.6
teleportprob = 0

dim red(colonies)
dim green(colonies)
dim blue(colonies)

' Draw colours for the various colonies...
' You should set these for every colony (else they'll be jet black)

red(1) = 65535

red(2) = 65535

red(3) = 65535

red(4) = 65535
green(4) = 20000

red(5) = 65535
green(5) = 20000

' ' ' ' ' ' ' ' ' ' ' ' ' '

randomize timer

dim storedx(colonies, store)
dim storedy(colonies, store)

x1 = (screen width / 2) - (width / 2)
y1 = ((screen height / 2) + (y_offset / 2)) - (depth / 2)
x2 = (screen width / 2) + (width / 2)
y2 = ((screen height / 2) + (y_offset / 2)) + (depth / 2)

resize console x1, y1, x2, y2
cls

dim x(colonies)
dim y(colonies)

for i = 1 to colonies
   x(i) = int(width / 2)
   y(i) = int(depth / 2)
   storedx(i, 1) = x(i)
   storedy(i, 1) = y(i)
next i

n = 1

main:
if inkey$ = "q" or inkey$ = "Q" or inkey$ = chr$(27) then
   disable done
   end
end if

for i = 1 to colonies

   if fadeoldflag and rnd < overdrawprob and (buttonflag < store) then
      forecolor 0, 0, 0
      plot storedx(i, n), storedy(i, n)
   end if

   if rnd < teleportprob then
      x(i) = int(rnd * width)
      y(i) = int(rnd * depth)
   else
      if rnd < 0.5 then x(i) = x(i) + jumpsize else x(i) = x(i) - jumpsize
      if x(i) < 0 then x(i) = width - 1
      if x(i) > width - 1 then x(i) = 0
      if rnd < 0.5 then y(i) = y(i) + jumpsize else y(i) = y(i) - jumpsize
      if y(i) < 0 then y(i) = depth - 1
      if y(i) > depth - 1 then y(i) = 0
   end if
   
   storedx(i, n) = x(i)
   storedy(i, n) = y(i)

   if button = 0 then
      forecolor red(i), green(i), blue(i)
      plot x(i), y(i)
   end if

next i

n = n + 1
if n > store then
   n = 1
   fadeoldflag = 1
end if

if button then
   if buttonflag < store then buttonflag = buttonflag + 1
else
   buttonflag = 0
end if

pauseloop:
if inkey$ <> "p" and inkey$ <> "P" then goto main else goto pauseloop