those black lines are not intentional.  i suspect they are some error with my home-brewed scaling function.  Because my blending function is operating on every pixel of each tile, I need to employ some mip-mapping to reduce the time it takes to complete based upon the number of total number tiles being displayed at any time.  Smaller tiles are not just scaled by gosu, but are using lower res versions of the tileset.  without this scaling function there are no little black lines; although it would take forever to blend up to four 1024x1024 textures per tile.

That said, if i do fix this scaling function, I'd likely want to switch between the two versions, as sometimes it might be handy to see the boarders between tiles, depending on what sort of game comes out of this.  'There are no mistakes, only happy accidents!'

I'm interested how others might approach scaling/mip-mapping?  here is mine, belongs to an instance of Surface class, and takes a float between 0.0 and 1.0 as input:

`
def scale(n)
nw = (@w*n).to_i
nh = (@h*n).to_i
skipw = (@w/nw)*4
skiph = (@h/nh)*4
pixie = ''
nh.times{|y|
  nw.times{|x|
   pixie << @pixels[((y*skiph)*@w)+(x*skipw),4]
  }
}
@w = nw
@h = nh
@pixels = pixie
return self
end
'
pixels, here, being the same as blob.