Conway's Game of Life with colors

When I first started messing with LÖVE, one of the first examples I gravitated towards was this Game of Life with colors. I just went back to it and ported it to Lua Carousel. Very fun. In the process I spent some time understanding its rules for assigning colors:

• Only live cells have a color.
• Initially live cells get random colors.
• Cells with 2 live neighbors continue to live and preserve their colors.
• Cells with 3 live neighbors are 'reborn' with the color of one of their 'parents'.
• Cells that die (fewer than 2 or greater than 3 live neighbors) stop spreading their color.

The link above also adds some randomness when cells are born, but I took it out to better see the interactions between "lineages" of cells.

math.randomseed(os.time())
N = 6
W, H = Safe_width/N, Safe_height/N
curr, new = {}, {}
for x=1,W do
  table.insert(curr, {})
  table.insert(new, {})
  for y=1,H do
    table.insert(curr[x], {v=0, c={0,0,0}})
    table.insert(new[x], {v=0, c={0,0,0}})
  end end
-- R pentomino
function set(x,y)
  curr[x][y].v = 1
  curr[x][y].c = {rand()/2+0.25, rand()/2+0.25, rand()/2+0.25}
end
cx = math.floor(W/2)
cy = math.floor(H/2)
set(cx, cy)
set(cx, cy+1)
set(cx, cy+2)
set(cx-1, cy)
set(cx+1, cy+1)
function car.draw()
  for x=1,W do
    for y=1,H do
      if curr[x][y].v > 0 then
        color(unpack(curr[x][y].c))
        rect('fill', x*N, y*N, N-1,N-1)
      end end end end
function car.update(dt)
  step()
end
function step()
  for x=2,W-1 do
    for y=2,H-1 do
      local n = nghs(x,y)
      if n < 2 or n > 3 then
        new[x][y].v = 0
      elseif n == 2 then
        new[x][y].v = curr[x][y].v
        local c, oldc = new[x][y].c, curr[x][y].c
        c[1], c[2], c[3] = oldc[1], oldc[2], oldc[3]
      elseif n == 3 then
        new[x][y].v = 1
        -- copy some random live neighbor's color over
        local oldc = random_color(x,y)
        local c = new[x][y].c
        c[1], c[2], c[3] = oldc[1], oldc[2], oldc[3]
      end end end
  curr, new = new, curr
end
function nghs(x,y)
  return curr[x-1][y-1].v + curr[x-1][y].v + curr[x-1][y+1].v +
      curr[x][y-1].v + curr[x][y+1].v +
      curr[x+1][y-1].v + curr[x+1][y].v + curr[x+1][y+1].v
end
function random_color(x,y)
  local rgbs = {}
  maybe_append_color(x-1, y-1, rgbs)
  maybe_append_color(x-1, y, rgbs)
  maybe_append_color(x-1, y+1, rgbs)
  maybe_append_color(x, y-1, rgbs)
  maybe_append_color(x, y+1, rgbs)
  maybe_append_color(x+1, y-1, rgbs)
  maybe_append_color(x+1, y, rgbs)
  maybe_append_color(x+1, y+1, rgbs)
  return rgbs[rand(#rgbs)]
end
function maybe_append_color(x,y, out)
  if curr[x][y].v > 0 then table.insert(out, curr[x][y].c) end
end

If you try pasting this program into Lua Carousel, remember to first run the abbreviations on one of the example screens. Or if you've deleted that screen, here are the abbreviations this program uses:

g = love.graphics
rect = g.rectangle
color = g.setColor
rand = math.random