diff --git a/.gitignore b/.gitignore
index cded043..4770d49 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,2 +1,3 @@
 build/
-test/
\ No newline at end of file
+test/
+backup/
\ No newline at end of file
diff --git a/ai.lua b/ai.lua
index fec5ba0..d35750c 100644
--- a/ai.lua
+++ b/ai.lua
@@ -79,7 +79,7 @@ function t.draw( nodes )
 end
 
 function t.save( nodes )
-  return bmp.savePoints( nodes.all, "512rgb24" )
+  return bmp.ai( nodes.all )
 end
 
 return t
\ No newline at end of file
diff --git a/bmp.lua b/bmp.lua
index 1332c1a..fbc9923 100644
--- a/bmp.lua
+++ b/bmp.lua
@@ -1,48 +1,17 @@
 --Load and save the bmp formats used by DEFCON.
 local t = {}
+local assert = assert
+local print = print
+local error = error
+local table = table
+local math = math
 local love = assert( love )
-local lfs = love.filesystem
 
---FFI bit-twiddling stuff.
-local ffi = require 'ffi'
-local bit = require 'bit'
 
-local function getHeader( filename )
-  local offset = love.data.unpack( "<I4", assert(love.filesystem.read( "data", filename, 14 )), 11 )
-  local header, size = assert( love.filesystem.read( filename, offset ) )
-  print( "BMP HEADER", filename, size, "\n", string.byte( header, 1, size ) )
-  return header
-end
 
-local formats = {
-  ["512rgb24"] = {
-    header = getHeader( "data/earth/africa.bmp" ),
-    encode = function( r ) return math.floor( r * 255 ) end,
-    bytesPerPixel = 3,
-    w = 512,
-    h = 285,
-  },
-  ["512r4"]     = {
-    header = getHeader( "data/earth/sailable.bmp" ),
-    encode = function( r ) return math.floor( r * 255 / 16 )  end,
-    bytesPerPixel = 0.5,
-    w = 512,
-    h = 285,
-  },
-  ["800r4"]     = {
-    header = getHeader( "data/earth/travel_nodes.bmp" ),
-    encode = function( r ) return math.floor( r * 255 / 16 ) end,
-    bytesPerPixel = 0.5,
-    w = 800,
-    h = 400,
-  }
-}
+local test = {}
 
-function t.header( format )
-  return formats[format] and formats[format].header
-end
-
-function t.load( filename )
+function test.load( filename )
   local imgd = love.image.newImageData( filename )
   print( "LOADING BITMAP: ", filename, imgd:getSize(), imgd:getFormat(), imgd:getDimensions() )
   local img = love.graphics.newImage( imgd )
@@ -50,78 +19,149 @@ function t.load( filename )
   return img, imgd
 end
 
---maps an array of 1-byte pixel values  (numbers 0 to 15 inclusive)
---to an array of half-byte pixel values (which can be concatenated into a string)
---BUT don't touch the first element (which is assumed to be a header or something)
-local function foldByteArray( bytes )
-  local nybbles = { bytes[1] }
-  for j = 2, #bytes / 2 do
-    local a, b = bytes[ 2 * j - 2 ], bytes[ 2 * j - 1 ]
-    nybbles[j] = string.char( 16 * a + b )
-  end
-  return nybbles
+function test.bitmapToWorld( x, y )
+  local w, a = 360.0, 600.0 / 800.0
+  local h = 360.0 * a
+  x = w * ( x - 800 ) / 800 - w / 2 + 360
+  y = h * ( y - 600 ) / 600 + 180
+  return x, y
 end
 
-local function packTwentyFour( bytes )
-  local twentyFour = { bytes[1] }
-  for j = 2, #bytes do
-    twentyFour[j] = string.char( bytes[j], bytes[j], bytes[j] )
+function test.compareData( a, b )
+  if a == b then return true end
+  print( "lengths:", a:len(), b:len() )
+  local errors = 0
+  for i = 1, math.min( a:len(), b:len() ) do
+    local a, b = a:sub( i, i ), b:sub( i, i )
+    if a ~= b then
+      errors = errors + 1
+      print( "mismatch:", errors, i, string.byte( a ), string.byte( b ) )
+    end
+    if errors > 1000 then break end
   end
-  return twentyFour
+  error( "test failed. output bitmap does not match!" )
 end
 
-function t.save( data, format )
-  local w, h = data:getDimensions()
-  format = assert( formats[format] )
-  local bytes = { format.header }
-  format.byte = 0
-  local i = 2
-  for y = h - 1, 0, -1 do
-    for x = 0, w - 1 do
-      bytes[i] = format.encode( data:getPixel(x, y) )
-      i = i + 1
-    end  
-  end
-  if format.bytesPerPixel < 1 then bytes = foldByteArray( bytes )
-  else bytes = packTwentyFour( bytes ) end
-  return table.concat( bytes )
+function test.worldToBitmap( x, y )
+  x = 800 * ( x + 180 ) / 360
+  y = 600 + 800 * ( y - 180 ) / 360
+  return x, y
 end
 
---takes an array of world-space points in [-180, 180] x [-100, 100] 
---e.g { { x = 0.5, y = 0.5 }, { x = 0.4, y = 0.6 }, }, etc.
-function t.savePoints( points, format )
-  format = assert( formats[format] )
+local function getHeader( filename )
+  local offset = 2 + love.data.unpack( "<I4", assert(love.filesystem.read( "data", filename, 14 )), 11 )
+  local header, size = assert( love.filesystem.read( filename, offset ) )
+  print( "BMP HEADER", filename, size, "\n", string.byte( header, 1, size ) )
+  return header
+end
+
+--BGR24 format. Takes the input of Love2D's data:getPixel( x, y )
+--on paper we would only care about one channel because all of these images are grayscale,
+--but a few of the pixels in the game's default territories are not exactly gray,
+--so we do it like this to make sure our output is byte-faithful when saving an unmodified vanilla map
+local function bgrChar( r, g, b )
+  return string.char( math.floor( b * 255 ), math.floor( g * 255 ), math.floor( r * 255 ) )
+end
+
+
+local formats = {
+  ["africa"]     = {
+    header = getHeader( "data/earth/africa.bmp" ),
+    w = 512,
+    h = 285,
+  },
+  ["sailable"]     = {
+    header = getHeader( "data/earth/sailable.bmp" ),
+    w = 512,
+    h = 285,
+    --technically this information is in the header already but I don't want to write code to parse it since we only use this one header
+    palette = {
+      [0] = 0,
+      [8] = 1,
+      [20] = 2,
+      [33] = 3,
+      [49] = 4,
+      [90] = 5,
+      [139] = 6,
+      [169] = 7,
+      [189] = 8,
+      [206] = 9,
+      [214] = 10,
+      [222] = 11,
+      [231] = 12,
+      [239] = 13,
+      [247] = 14,
+      [255] = 15
+    },
+  },
+  ["travel"]     = {
+    header = getHeader( "data/earth/travel_nodes.bmp" ),
+    w = 800,
+    h = 400,
+  },
+  ["ai"]     = {
+    header = getHeader( "data/earth/ai_markers.bmp" ),
+    w = 512,
+    h = 285,
+  },
+}
+
+function formats.ai:test( )
+  print "testing ai nodes"
+  local filename = "data/earth/ai_markers.bmp" 
+  local img, imgd = test.load( filename )
+  local idx = 1
+  local nodes = {}
+  for x = 0, 511 do
+    for y = 0, 284 do
+      local r, g = imgd:getPixel( x, 284 - y )
+      if r > 0.5 or g > 0.5 then
+        local long = x * (360 / imgd:getWidth()) - 180
+        local lat = y * (200 / img:getHeight()) - 100
+        local attacking = (r > 0.5)
+        local node = {x = long, y = lat, attacking = attacking, idx = idx}
+        print( "ai marker", idx, x, y, long, lat )
+        nodes[ idx ] = node
+        idx = idx + 1
+      end
+    end
+  end
+
+  local encodedString = self:encode( nodes )
+  love.filesystem.write( "ai_markers.bmp", encodedString )
+
+  local eimg, eimgd = test.load( "ai_markers.bmp" ) --the one we just saved
+  for x = 0, 511 do
+    for y = 0, 284 do
+      local r, g = imgd:getPixel( x, 284 - y )
+      local er, eg = eimgd:getPixel( x, 284 - y )
+      if math.max( r, g, er, eg ) > 0.5 then
+        print( "node pixel: ", x, 284 - y, r, g, er, eg )
+        assert( ( r > 0.5 and er > 0.5 ) or ( g > 0.5 and eg > 0.5 ), "ai marker mismatch!" )
+      end
+    end
+  end
+  print( "ai markers OK" )
+end
+
+function formats.ai:encode( data )
 
   --set up bitmap as an array of pixels
-  local w, h = format.w, format.h
-  local size = 2 + format.w * format.h
-  local bitmap = { format.header }
+  local w, h = self.w, self.h
+  local size = 2 + self.w * self.h
+  local bitmap = { self.header:sub( 1, -3 ) }
   for j = 2, size do bitmap[j] = 0 end
 
-  --this is black-and-white only. easy case
-  if format.bytesPerPixel < 1 then
-    for i, point in ipairs( points ) do
-      local wx, wy = point.x, point.y
-      -- get bitmap coordinates:
-      -- N.B., y's divided by 190 rather than 200 because of an idiosyncracy in the travel node image
-      local x, y = math.floor(format.w * (wx + 180) / 360), math.floor(format.h * (wy + 100) / 190)
 
-      --get index into byte array
-      local idx = 2 + y * format.w + x
-      print( "SAVING POINT:", wx, wy, x, format.h - y - 1, idx )
-      bitmap[idx] = 1 --white: this header uses an indexed palette
-    end
-    --now map pixels to 4-bit strings, slap on the header, and pass it back up
-    return table.concat( foldByteArray( bitmap ) )
-  end
-
-  --cf. ai.lua: these points can be red or green
-  for i, point in ipairs( points ) do
+  for i, point in ipairs( data ) do
     local wx, wy = point.x, point.y
     --get bitmap coordinates
-    local x, y = math.floor(format.w * (wx + 180) / 360), math.floor(format.h * (1.0 - (wy + 100) / 200))
+    local x = math.floor(self.w * (wx + 180) / 360)
+    --idk why exactly I need to round the value here instead of truncating it
+    local y = math.floor(0.5 + self.h * (wy + 100) / 200)
+    print( "export ai marker", i, x, y, wx, wy )
     --get index into byte array
-    local idx = 2 + x * format.h + y
+    local idx = 2 + y * self.w + x
     --in-editor we could have two points in the same place, possibly of the same or different types
     --in case we miss something upstream, don't corrupt these duplicate points,
     --just saturate the attack/defense value
@@ -142,4 +182,138 @@ function t.savePoints( points, format )
 
   return table.concat( bitmap )
 end
+
+function formats.travel:test()
+  print "testing travel nodes"
+  local filename = "data/earth/travel_nodes.bmp" 
+  local img, imgd = test.load( filename )
+  local nodes = {}
+  local n = 1
+  for x = 0, 799 do
+    for y = 0, 399 do
+      if imgd:getPixel( x, 399 - y ) > 0 then
+        local long, lat = test.bitmapToWorld( x, y )
+        nodes[n] = {x = long, y = lat, idx = n}
+        print( "read:", n, long, lat, x, y )
+        n = n + 1
+      end
+    end
+  end
+
+  print( "loaded ", n, "nodes" )
+  local encodedString = self:encode( nodes )
+  test.compareData( love.filesystem.read( filename ), encodedString )
+  love.filesystem.write( "travel_nodes.bmp", encodedString )
+  print( "travel nodes OK" )
+end
+
+--Sparse bitmap with a few white pixels.
+function formats.travel:encode( points )
+  --set up bitmap as an array of 8-bit pixels
+  local w, h = self.w, self.h
+  local size = 2 + w * h
+  local bitmap = { self.header }
+  for j = 2, size do bitmap[j] = 0 end
+
+  --write white pixels
+  for i, point in ipairs( points ) do
+    local wx, wy = point.x, point.y
+    -- get bitmap coordinates:
+    local x = 800 * ( wx + 180 ) / 360
+    local y = 600 + 800 * ( wy - 180 ) / 360
+    local offset = math.floor( y * self.w + x - 2 )
+    --1 := white
+    bitmap[offset] = 1
+    print( "encoded:", point.idx, wx, wy, x, y )
+  end
+
+  --fold into 4-bit pixel array
+  local nybbles = { bitmap[1] }
+  for j = 2, size / 2 do
+    local a, b = bitmap[ 2 * j - 2 ], bitmap[ 2 * j - 1 ]
+    nybbles[j] = string.char( 16 * a + b )
+  end
+
+  return table.concat( nybbles )
+end
+
+function formats.sailable:test()
+  print "testing sailable"
+  local filename = "data/earth/sailable.bmp" 
+  local img, imgd = test.load( filename )
+  local encoded = self:encode( imgd )
+  love.filesystem.write( "sailable_out.bmp", encoded )
+  test.compareData( love.filesystem.read( filename ), encoded )
+  print "sailable OK"
+end
+
+function formats.sailable:encode( data )
+  local w, h = self.w, self.h
+  local bytes = { self.header:sub( 1, -2 ) }
+  local i = 2
+
+  --y coordinates are written top to bottom
+  for y = h - 1, 0, -1 do
+    for x = 0, w - 1 do
+      bytes[i] = assert( self.palette[ math.floor( data:getPixel(x, y) * 255 )] )
+      i = i + 1
+    end  
+  end
+
+  --fold into 4-bit pixel array
+  local nybbles = { bytes[1] }
+  for j = 2, #bytes / 2 do
+    local a, b = bytes[ 2 * j ], bytes[ 2 * j + 1 ]
+    nybbles[j] = string.char( 16 * a + b )
+  end
+
+  return table.concat( nybbles )
+end
+
+function formats.africa:test()
+  print "testing africa"
+  local filename = "data/earth/africa.bmp" 
+  local img, imgd = test.load( filename )
+  local encoded = self:encode( imgd )
+  love.filesystem.write( "africa_out.bmp", encoded )
+  test.compareData( love.filesystem.read( filename ), encoded )
+  print "africa OK"
+end
+
+
+function formats.africa:encode( data )
+  local w, h = self.w, self.h
+  local bytes = { self.header:sub( 1, -3 ) }
+  local i = 2
+
+  --y coordinates are written top to bottom
+  for y = h - 1, 0, -1 do
+    for x = 0, w - 1 do
+      bytes[i] = bgrChar( data:getPixel(x, y) )
+      i = i + 1
+    end  
+  end
+  return table.concat( bytes )
+end
+
+function t.load( filename )
+  local imgd = love.image.newImageData( filename )
+  print( "LOADING BITMAP: ", filename, imgd:getSize(), imgd:getFormat(), imgd:getDimensions() )
+  local img = love.graphics.newImage( imgd )
+  img:setFilter( "nearest", "nearest" )
+  return img, imgd
+end
+
+function t.save( data, format )
+  return assert(formats[format]):encode( data )
+end
+
+--convenience
+formats.territory = formats.africa
+for fmt, tbl in pairs( formats ) do
+  t[fmt] = function( data ) return tbl:encode( data ) end
+  --TESTING
+  tbl:test()
+end
+
 return t
\ No newline at end of file
diff --git a/map.lua b/map.lua
index a6cdfb5..7ed00f3 100644
--- a/map.lua
+++ b/map.lua
@@ -179,10 +179,12 @@ function map.draw()
 end
 
 local function write( filename, string )
+  --
   print( "Writing", string:len(), "bytes to", filename )
   os.rename( filename, filename..".bak" ) --just in case :^)
-  local file = assert( io.open( filename, "w+" ) )
+  local file = assert( io.open( filename, "wb+" ) )
   assert( file:write( string ) )
+  assert( file:flush() ) --your toilet is set to stun, not kill
   file:close()
 end
 
diff --git a/territory.lua b/territory.lua
index faa9cbd..bf0a7cf 100644
--- a/territory.lua
+++ b/territory.lua
@@ -143,9 +143,9 @@ function t.computeBorder( territory, threshold, key )
 end
 
 function t.save( territory )
-  local fmt = (territory.name == "sailable") and "512r4" or "512rgb24"
+  local fmt = (territory.name == "sailable") and "sailable" or "territory"
   print( "saving bitmap: ", territory.name, fmt )
-  return bmp.save( territory.imgd, fmt )
+  return bmp[fmt]( territory.imgd )
 end
 
 return t
\ No newline at end of file
diff --git a/travelNodes.lua b/travelNodes.lua
index 59a01d5..5612873 100644
--- a/travelNodes.lua
+++ b/travelNodes.lua
@@ -153,7 +153,7 @@ function t.drawConnections( nodes )
 end
 
 function t.save( nodes )
-  return bmp.savePoints( nodes.nodes, "800r4")
+  return bmp.travel( nodes.nodes )
 end
 
 return t
\ No newline at end of file