function param1()
  return "fore width", 1, 100, 3
end

function param2()
  return "bg width", 1, 100, 3
end

function circle( mx, my, w )

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

  local p1 = bs_param1()
  local p2 = bs_param2()
  local n = p1 + p2
  local sx = mx - w
  local dx = mx + w

  local x
  for x=sx,dx do

    local px = x - mx
    local s = w*w - px*px

    if s > 0 then
      s = math.sqrt( s )
      local ly = my - s
      local ry = my + s

      local r,g,b = bs_bg()
      if x % n < p1 then
        r,g,b = bs_fore()
      end

      bs_rect( x,ly, 1, (ry-ly), r,g,b,255 )
    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