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remstart
== Conway's Game of Life ==
== By Oli Burt ==

Rules:
Any live cell with fewer than two live neighbours dies, as if caused by under-population.
Any live cell with two or three live neighbours lives on to the next generation.
Any live cell with more than three live neighbours dies, as if by overcrowding.
Any dead cell with exactly three live neighbours becomes a live cell, as if by reproduction.
/Rules

I will store the entire ruleset in a single binary number, using it as a sort of stack. I will use
bitwise manipulation, using the number of neighbouring cells as a parameter, to push the ruleset value
along to the appropriate bit for that number of neighbours, then applying &&1 will give the correct output.
The rules are slightly different for live and dead cells, so I will have to examine this.
If I cannot resolve the difference I will use two ruleset values, one for live and one for dead.

Live Cell Neighbours:
876543210
000001100

Dead Cell Neighbours:
876543210
000001000

I can't figure out how to resolve the difference so I'll use two values.

It has occured to me that copying the entire world at once is uneconomic. By making a third world array
I could update one buffer while using the other to update the world.
remend

set display mode 1024,768,32

global surviverule =12
global birthrule =8

rem create world
global xmax = 799
global ymax = 699
dim grid(xmax,ymax)
dim gbuff(xmax,ymax) :`gbuff stores a copy of the world for reference when updating, so that grid can be changed without effecting the results.
populate()

rem colours
dim colour(1)
colour(0) = 120
colour(1) = rgb(255,255,255)

delay = 0
time = timer()

set text font "verdana",1
set text size 14

rem == Main ==
do
  gosub inputs
  cls  
  gosub display_text
  display_world()
    
  rem Update world after delay    
  if time+delay < timer()
    time=timer()
    inc gen
    copy_world()
    update_world()
  endif
loop

end

rem == Subroutines ==
display_text:
  ink colour(1),0
  text xmax+10,0,"Generations: "+str$(gen)
  text xmax+10,20,"Delay: " + str$(delay)+"ms"
  text xmax+10,40,"SHIFT/CTRL adjusts delay"
  text xmax+10,81,"Survival Ruleset: "+str$(surviverule)
  text xmax+10,100,"BIN: "+right$(bin$(surviverule),9)
  text xmax+10,120,"L/R to change"
  text xmax+10,160,"Birth Ruleset: "+str$(birthrule)
  text xmax+10,182,"BIN: "+right$(bin$(birthrule),9)
  text xmax+10,200,"UP/DOWN to change"
  text xmax+10,240,"Press ENTER to re-populate"
return
`//

inputs:
  delay = delay + (shiftkey() - controlkey())*10
  if delay <0 then delay=0  
  surviverule = surviverule + rightkey() - leftkey()
  if surviverule <1 then surviverule = 1
  if surviverule >511 then surviverule = 511
  birthrule = birthrule + upkey() - downkey()
  if birthrule <1 then birthrule = 1
  if birthrule >511 then birthrule = 511
  if returnkey() = 1 then populate() : gen=0
return

rem == Functions ==
function populate()
  for y = 0 to ymax
    for x = 0 to xmax
      grid(x,y) = rnd(1)
    next x
  next y
endfunction
`//

function copy_world()
  for y = 0 to ymax
      for x = 0 to xmax
        gbuff(x,y) = grid(x,y)
      next x
    next y
endfunction
`//

function update_world()
  for y = 0 to ymax
    for x = 0 to xmax
      rem prepare check-boundaries for cell x,y
      rem (these assignments use logic to make sure they stay in bounds)
      vmin = 0-(y>0)
      vmax = y < ymax
      umin = 0-(x>0)
      umax = x < xmax
        
      rem check for neighbours of x,y
      nbrs = 0
      for v = vmin to vmax
        for u = umin to umax
          if u<>0 or v<>0 then nbrs = nbrs + gbuff(x+u,y+v) :`check we don't include x,y as its own neighbour.
        next u
      next v
        
      rem update cell x,y
      if gbuff(x,y) = 0
        grid(x,y) = (birthrule >> nbrs) && 1
      else
        grid(x,y) = (surviverule >> nbrs) && 1
      endif
    next x
  next y
endfunction
`//

function display_world()
  lock pixels
  for y = 0 to ymax
    for x = 0 to xmax
      ink colour(grid(x,y)),0
      dot x,y
    next x
  next y
  unlock pixels
endfunction
`//