function param1()
  return "width", 1, 100, 4
end

function param2()
  return "height", 1, 100, 4
end

function circle( mx, my, w )

  mx = math.floor( mx )
  my = math.floor( my )
  w = math.ceil( w )

  local sy = my - w
  local dy = my + w

  local cx = bs_param1() * 2
  local cy = bs_param2() * 2
  local nx = cx / 2
  local ny = cy / 2

  local x,y
  for y=sy,dy do

    local py = y - my
    local s = w*w - py*py

    if s > 0 then
      s = math.ceil( math.sqrt( s ) )
      local lx = mx - s
      local rx = mx + s

      local by = 0
      local sy = y % cy
      if sy < ny then
        by = 1
      end

      for x=lx,rx do

        local bx = 0
        local sx = x % cx
        if sx < nx then
          bx = 1
        end

        local r,g,b = bs_fore()

        local n = (bx + by) % 2
        if n == 1 then
          r,g,b = bs_bg()
        end

        bs_pixel_set( x,y, r,g,b,255 )
      end

    end
  end
end

function main( x, y, p )

  local w = bs_width()
  if w < 0.25 then
    w = 0.25
  end

  local updateDist = w / 2
  if w > 5 then
    updateDist = w/4
  end
  if w > 20 then
    updateDist = w/10
  end
  if w > 100 then
    updateDist = w/14
  end

  if not firstDraw then
    local distance = bs_distance( lastDrawX - x, lastDrawY - y )
    if distance < updateDist then
      return 0
    end
  end

  circle( x,y, w )

  lastDrawX = x
  lastDrawY = y
  firstDraw = false

  return 1
end

lastDrawX = 0
lastDrawY = 0
firstDraw = true