local cos, sin, floor, pi = math.cos, math.sin, math.floor, math.pi

function Bitmap:render()
  for y = 1, self.height do
    print(table.concat(self.pixels[y]))
  end
end

function Bitmap:pentagram(x, y, radius, rotation, outlcolor, fillcolor)
  local function pxy(i) return x+radius*cos(i*pi*2/5+rotation), y+radius*sin(i*pi*2/5+rotation) end
  local x1, y1 = pxy(0)
  for i = 1, 5 do
    local x2, y2 = pxy(i*2)