diff --git a/Makefile b/Makefile
index ad6a9a5..0da53ea 100644
--- a/Makefile
+++ b/Makefile
@@ -14,11 +14,11 @@ UNINSTALL_VERSION=
 MOON_FILES= code_obj.moon error_handling.moon files.moon nomsu.moon nomsu_compiler.moon \
 			syntax_tree.moon containers.moon bitops.moon parser.moon pretty_errors.moon \
 			text.moon nomsu_decompiler.moon nomsu_environment.moon bootstrap.moon \
-			builtin_metatables.moon
+			builtin_metatables.moon colors.moon
 LUA_FILES= code_obj.lua error_handling.lua files.lua nomsu.lua nomsu_compiler.lua \
 		   syntax_tree.lua containers.lua bitops.lua parser.lua pretty_errors.lua \
 		   text.lua nomsu_decompiler.lua nomsu_environment.lua bootstrap.lua \
-		   builtin_metatables.lua
+		   builtin_metatables.lua colors.lua
 CORE_NOM_FILES=$(shell cat lib/core/init.nom | sed -n 's;export "\(.*\)";lib/\1.nom;p') lib/core/init.nom
 CORE_LUA_FILES= $(patsubst %.nom,%.lua, $(CORE_NOM_FILES))
 COMPAT_NOM_FILES=$(wildcard lib/compatibility/*.nom)
diff --git a/error_handling.lua b/error_handling.lua
index fd6572e..b7d5d13 100644
--- a/error_handling.lua
+++ b/error_handling.lua
@@ -1,14 +1,7 @@
 local debug_getinfo = debug.getinfo
 local Files = require("files")
+local C = require("colors")
 local pretty_error = require("pretty_errors")
-local RED = "\027[31m"
-local BRIGHT_RED = "\027[31;1m"
-local RESET = "\027[0m"
-local YELLOW = "\027[33m"
-local CYAN = "\027[36m"
-local GREEN = "\027[32m"
-local BLUE = "\027[34m"
-local DIM = "\027[37;2m"
 local ok, to_lua = pcall(function()
   return require('moonscript.base').to_lua
 end)
@@ -66,10 +59,10 @@ debug.getinfo = function(thread, f, what)
 end
 local enhance_error
 enhance_error = function(error_message, start_fn, stop_fn)
-  if not (error_message and error_message:match("\x1b")) then
+  if not (error_message and error_message:match("%d|")) then
     error_message = error_message or ""
     do
-      local fn = error_message:match("attempt to call a nil value %(global '(.*)'%)")
+      local fn = (error_message:match("attempt to call a nil value %(global '(.*)'%)") or error_message:match("attempt to call global '(.*)' %(a nil value%)"))
       if fn then
         error_message = "The action '" .. tostring(fn:from_lua_id()) .. "' is not defined."
       end
@@ -130,7 +123,7 @@ enhance_error = function(error_message, start_fn, stop_fn)
     end
   end
   local ret = {
-    tostring(RED) .. "ERROR: " .. tostring(BRIGHT_RED) .. tostring(error_message or "") .. tostring(RESET),
+    C('bold red', error_message or "Error"),
     "stack traceback:"
   }
   local level = 2
@@ -181,10 +174,10 @@ enhance_error = function(error_message, start_fn, stop_fn)
           do
             local err_line = lines[calling_fn.currentline]
             if err_line then
-              local offending_statement = tostring(BRIGHT_RED) .. tostring(err_line:match("^[ ]*(.*)")) .. tostring(RESET)
-              line = tostring(YELLOW) .. tostring(filename) .. ":" .. tostring(calling_fn.currentline) .. " in " .. tostring(name) .. "\n        " .. tostring(offending_statement) .. tostring(RESET)
+              local offending_statement = C('bright red', err_line:match("^[ ]*(.*)"))
+              line = C('yellow', tostring(filename) .. ":" .. tostring(calling_fn.currentline) .. " in " .. tostring(name) .. "\n        " .. tostring(offending_statement))
             else
-              line = tostring(YELLOW) .. tostring(filename) .. ":" .. tostring(calling_fn.currentline) .. " in " .. tostring(name) .. tostring(RESET)
+              line = C('yellow', tostring(filename) .. ":" .. tostring(calling_fn.currentline) .. " in " .. tostring(name))
             end
           end
         else
@@ -236,20 +229,20 @@ enhance_error = function(error_message, start_fn, stop_fn)
           if file and (calling_fn.short_src:match("%.moon$") or file:match("^#![^\n]*moon\n")) and type(MOON_SOURCE_MAP[file]) == 'table' then
             local char = MOON_SOURCE_MAP[file][calling_fn.currentline]
             line_num = file:line_number_at(char)
-            line = tostring(CYAN) .. tostring(calling_fn.short_src) .. ":" .. tostring(line_num) .. " in " .. tostring(name or '?') .. tostring(RESET)
+            line = C('cyan', tostring(calling_fn.short_src) .. ":" .. tostring(line_num) .. " in " .. tostring(name or '?'))
           else
             line_num = calling_fn.currentline
             if calling_fn.short_src == '[C]' then
-              line = tostring(GREEN) .. tostring(calling_fn.short_src) .. " in " .. tostring(name or '?') .. tostring(RESET)
+              line = C('green', tostring(calling_fn.short_src) .. " in " .. tostring(name or '?'))
             else
-              line = tostring(BLUE) .. tostring(calling_fn.short_src) .. ":" .. tostring(calling_fn.currentline) .. " in " .. tostring(name or '?') .. tostring(RESET)
+              line = C('blue', tostring(calling_fn.short_src) .. ":" .. tostring(calling_fn.currentline) .. " in " .. tostring(name or '?'))
             end
           end
           if file then
             do
               local err_line = lines[line_num]
               if err_line then
-                local offending_statement = tostring(BRIGHT_RED) .. tostring(err_line:match("^[ ]*(.*)$")) .. tostring(RESET)
+                local offending_statement = C('bright red', tostring(err_line:match("^[ ]*(.*)$")))
                 line = line .. ("\n        " .. offending_statement)
               end
             end
@@ -258,7 +251,7 @@ enhance_error = function(error_message, start_fn, stop_fn)
       end
       table.insert(ret, line)
       if calling_fn.istailcall then
-        table.insert(ret, "      " .. tostring(DIM) .. "(...tail calls...)" .. tostring(RESET))
+        table.insert(ret, C('dim', "      (...tail calls...)"))
       end
       _continue_0 = true
     until true
diff --git a/error_handling.moon b/error_handling.moon
index 18ae4ef..ebd8309 100644
--- a/error_handling.moon
+++ b/error_handling.moon
@@ -1,18 +1,10 @@
 -- This file contains the logic for making nicer error messages
 debug_getinfo = debug.getinfo
 Files = require "files"
+C = require "colors"
 pretty_error = require("pretty_errors")
 export SOURCE_MAP
 
-RED = "\027[31m"
-BRIGHT_RED = "\027[31;1m"
-RESET = "\027[0m"
-YELLOW = "\027[33m"
-CYAN = "\027[36m"
-GREEN = "\027[32m"
-BLUE = "\027[34m"
-DIM = "\027[37;2m"
-
 ok, to_lua = pcall -> require('moonscript.base').to_lua
 if not ok then to_lua = -> nil
 MOON_SOURCE_MAP = setmetatable {},
@@ -47,9 +39,11 @@ debug.getinfo = (thread,f,what)->
     return info
 
 enhance_error = (error_message, start_fn, stop_fn)->
-    unless error_message and error_message\match("\x1b")
+    -- Hacky: detect the line numbering
+    unless error_message and error_message\match("%d|")
         error_message or= ""
-        if fn = error_message\match("attempt to call a nil value %(global '(.*)'%)")
+        if fn = (error_message\match("attempt to call a nil value %(global '(.*)'%)") or
+            error_message\match("attempt to call global '(.*)' %(a nil value%)"))
             error_message = "The action '#{fn\from_lua_id!}' is not defined."
         level = 2
         while true
@@ -91,7 +85,7 @@ enhance_error = (error_message, start_fn, stop_fn)->
 
 
     ret = {
-        "#{RED}ERROR: #{BRIGHT_RED}#{error_message or ""}#{RESET}"
+        C('bold red', error_message or "Error")
         "stack traceback:"
     }
 
@@ -125,10 +119,10 @@ enhance_error = (error_message, start_fn, stop_fn)->
             file = Files.read(filename)
             lines = file and file\lines! or {}
             if err_line = lines[calling_fn.currentline]
-                offending_statement = "#{BRIGHT_RED}#{err_line\match("^[ ]*(.*)")}#{RESET}"
-                line = "#{YELLOW}#{filename}:#{calling_fn.currentline} in #{name}\n        #{offending_statement}#{RESET}"
+                offending_statement = C('bright red', err_line\match("^[ ]*(.*)"))
+                line = C('yellow', "#{filename}:#{calling_fn.currentline} in #{name}\n        #{offending_statement}")
             else
-                line = "#{YELLOW}#{filename}:#{calling_fn.currentline} in #{name}#{RESET}"
+                line = C('yellow', "#{filename}:#{calling_fn.currentline} in #{name}")
         else
             local line_num
             if name == nil
@@ -161,21 +155,21 @@ enhance_error = (error_message, start_fn, stop_fn)->
             if file and (calling_fn.short_src\match("%.moon$") or file\match("^#![^\n]*moon\n")) and type(MOON_SOURCE_MAP[file]) == 'table'
                 char = MOON_SOURCE_MAP[file][calling_fn.currentline]
                 line_num = file\line_number_at(char)
-                line = "#{CYAN}#{calling_fn.short_src}:#{line_num} in #{name or '?'}#{RESET}"
+                line = C('cyan', "#{calling_fn.short_src}:#{line_num} in #{name or '?'}")
             else
                 line_num = calling_fn.currentline
                 if calling_fn.short_src == '[C]'
-                    line = "#{GREEN}#{calling_fn.short_src} in #{name or '?'}#{RESET}"
+                    line = C('green', "#{calling_fn.short_src} in #{name or '?'}")
                 else
-                    line = "#{BLUE}#{calling_fn.short_src}:#{calling_fn.currentline} in #{name or '?'}#{RESET}"
+                    line = C('blue', "#{calling_fn.short_src}:#{calling_fn.currentline} in #{name or '?'}")
 
             if file
                 if err_line = lines[line_num]
-                    offending_statement = "#{BRIGHT_RED}#{err_line\match("^[ ]*(.*)$")}#{RESET}"
+                    offending_statement = C('bright red', "#{err_line\match("^[ ]*(.*)$")}")
                     line ..= "\n        "..offending_statement
         table.insert ret, line
         if calling_fn.istailcall
-            table.insert ret, "      #{DIM}(...tail calls...)#{RESET}"
+            table.insert ret, C('dim', "      (...tail calls...)")
 
     return table.concat(ret, "\n")
 
diff --git a/lib/consolecolor/init.nom b/lib/consolecolor/init.nom
index 27823b8..606f4b6 100644
--- a/lib/consolecolor/init.nom
+++ b/lib/consolecolor/init.nom
@@ -17,9 +17,12 @@ $colors = {
 }
 
 for $name = $colornum in $colors:
-    $colornum = "\$colornum"
-    \($name \$text) compiles to:
-        if $text:
-            return (Lua "('\\027[\($colornum)m'..\($text as lua expr)..'\\027[0m')")
-        ..else:
-            return (Lua "'\\027[\($colornum)m'")
+    (nomsu environment).($name, as lua id) =
+        for $text:
+            if $(COLOR ENABLED):
+                if $text:
+                    return "\x1B[\($colornum)m\$text\x1b[0m"
+                ..else:
+                    return "\x1B[\($colornum)m"
+            ..else:
+                return ($text or "")
diff --git a/lib/core/errors.nom b/lib/core/errors.nom
index b1f1941..6be7e7f 100644
--- a/lib/core/errors.nom
+++ b/lib/core/errors.nom
@@ -75,6 +75,7 @@ use "core/control_flow"
 
 (assume $a == $b) parses as (assume ($a == $b))
 (assume $a != $b) parses as (assume ($a != $b))
+(test that $condition) parses as (assume $condition)
 
 test:
     try: fail
diff --git a/lib/progressbar/init.nom b/lib/progressbar/init.nom
index 98efe11..b3fb3a2 100644
--- a/lib/progressbar/init.nom
+++ b/lib/progressbar/init.nom
@@ -1,12 +1,25 @@
 #!/usr/bin/env nomsu -V6.15.13.8
 # A progress bar
-    
+use "consolecolor"
+
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+test:
+    assume (0 / 1 progress bar)
+    assume (10 wide 0.5 progress bar)
+
 external:
     ($x / $w progress bar) means:
         $x = ($x clamped between 0 and $w)
-        $bits = [" ", "▏", "▎", "▍", "▌", "▋", "▊", "▉", "█"]
-        $middle = ("" if ($x == $w) else $bits.(1 + (floor ((#$bits) * ($x mod 1)))))
-        return ("
-            \027[0m[\027[32;40m\($bits, last, rep (floor $x))\$middle\(" ", rep ($w - ((floor $x) + 1)))\027[0m]
-        ")
+        if $(COLOR ENABLED):
+            $bits = [" ", "▏", "▎", "▍", "▌", "▋", "▊", "▉", "█"]
+            $middle = ("" if ($x == $w) else $bits.(1 + (floor ((#$bits) * ($x mod 1)))))
+            return ("
+                \(reset color)[\(green)\($bits, last, rep (floor $x))\$middle\(" ", rep ($w - ((floor $x) + 1)))\(reset color)]
+            ")
+        ..else:
+            # Probably not unicode support either:
+            return ("
+                [\("#", rep ($x, rounded down))\("-", rep ($w - ($x, rounded down)))]
+            ")
     ($w wide $ progress bar) means (($ * $w) / $w progress bar)
diff --git a/lib/tools/repl.nom b/lib/tools/repl.nom
index 3d2318c..029df4a 100755
--- a/lib/tools/repl.nom
+++ b/lib/tools/repl.nom
@@ -52,7 +52,8 @@ command line program with $args:
             if (($line == "\n") or (not $line)):
                 if ((size of $buff) > 0):
                     # clear the line
-                    say "\027[1A\027[2K" inline
+                    if $(COLOR ENABLED):
+                        say "\027[1A\027[2K" inline
                 go to (run buffer)
             $buff, add ($line, with "\t" -> "    ")
             say (dim (yellow ".. ")) inline
diff --git a/lib/tools/tutorial.nom b/lib/tools/tutorial.nom
index 7c7d39c..dd26ada 100755
--- a/lib/tools/tutorial.nom
+++ b/lib/tools/tutorial.nom
@@ -25,11 +25,11 @@ $lessons = [
     lesson "Variables":
         # In Nomsu, variables have a "$" prefix, and you can just assign to them
             without declaring them first:
-        $x = 10
-        assume ($x == 10)
+        $x = 1
+        test that ($x == 1)
         
         # Variables which have not yet been set have the value (nil)
-        assume ($foobar == (nil))
+        test that ($foobar == (nil))
         
         # Variables can be nameless:
         $ = 99
@@ -40,16 +40,15 @@ $lessons = [
         # Figure out what value $my_var should have:
         $my_var = 100
         $my_var = ($my_var + $x + $(my favorite number))
-        assume ($my_var == (???))
+        test that ($my_var == (???))
     
     lesson "Actions":
-        # Fix this action so the tests pass, then save and quit.
-        # If the tests don't pass, you can come back to this file later.
+        # Fix this action so the tests pass:
         ($x doubled) means ((???) * $x)
         
         # Tests:
-        assume ((2 doubled) == 4)
-        assume ((-5 doubled) == -10)
+        test that ((2 doubled) == 4)
+        test that ((-5 doubled) == -10)
     
     lesson "Blocks":
         # When you need to do multiple things inside an action, use a block.
@@ -64,6 +63,32 @@ $lessons = [
             $correct_answer = (4 * ($num * $num))
             if (($num doubled then squared) != $correct_answer):
                 fail "Wrong answer for \($num)!"
+
+    lesson "Text":
+        # Nomsu text is enclosed in double quotation marks:
+        $text = "Hello"
+        
+        # You can insert values into text using a backslash:
+        test that ("two plus three is \(2 + 3)" == (???))
+        
+        # Variables don't require parentheses, but other expressions do:
+        $x = 99
+        test that ("$x is \$x" == (???))
+        
+        # This can be used to convert values to text:
+        test that ("\$x" == (???))
+        
+        # Longer strings use '("' followed by an indented region:
+        $long = ("
+            line one
+              line two with spaces at the front
+        ")
+        
+        test that
+            $long == ("
+                \(<your code here>)
+                \(<your code here>)
+            ")
     
     lesson "Conditionals":
         # Make this action return "big" if its argument
@@ -75,11 +100,11 @@ $lessons = [
                 <your code here>
         
         # Tests:
-        for $small_number in [0, 1, -5, -999, 99]:
-            assume ((the size of $small_number) == "small")
-        
         for $big_number in [9999, 100]:
-            assume ((the size of $big_number) == "big")
+            test that ((the size of $big_number) == "big")
+
+        for $small_number in [0, 1, -5, -999, 99]:
+            test that ((the size of $small_number) == "small")
     
     lesson "Loops":
         # Fix this action so the tests pass:
@@ -93,14 +118,14 @@ $lessons = [
             return $sum
         
         # Tests:
-        assume ((the sum of [1, 2, 3, 4, 5]) == 15)
-        assume ((the sum of [100, 200]) == 300)
+        test that ((the sum of [1, 2, 3, 4, 5]) == 15)
+        test that ((the sum of [100, 200]) == 300)
         
         # You can also loop over a number range like this:
         $total = 0
         for $i in 1 to 3:
             $total = ($total + $i)
-        assume ($total == (???))
+        test that ($total == (???))
     
     lesson "Variable Scopes":
         # Nomsu's variables are local by default, and actions have their own scopes:
@@ -111,17 +136,17 @@ $lessons = [
         (do something) means:
             # The variable $y is never set in this action, so it has the same value
                 it has outside this action.
-            assume ($y == (???))
+            test that ($y == (???))
             
             # $x is set inside this action, and actions have their own scopes.
             $x = $y
             
             # What number should $x be here?
-            assume ($x == (???))
+            test that ($x == (???))
         
         # After running the action, what value should $x have?
         do something
-        assume ($x == (???))
+        test that ($x == (???))
     
     lesson "More Variable Scopes":
         # Loops and conditionals do *not* have their own scopes:
@@ -131,13 +156,13 @@ $lessons = [
             $z = 2
         
         # After assigning in a conditional, what should $z be?
-        assume ($z == (???))
+        test that ($z == (???))
         for $ in 1 to 1:
             # Set $z inside a loop:
             $z = 3
         
         # After assigning in a loop, what should $z be?
-        assume ($z == (???))
+        test that ($z == (???))
     
     lesson "Externals":
         # The 'external' block lets you modify variables outside an action:
@@ -147,7 +172,7 @@ $lessons = [
         do something
         
         # After running the action that sets $x in an 'external' block, what should $x be?
-        assume ($x == (???))
+        test that ($x == (???))
     
     lesson "Locals":
         # The 'with' block lets you create a local scope for the variables you list:
@@ -158,8 +183,8 @@ $lessons = [
             $z = 2
         
         # After setting $y and $z in the 'with [$y]' block, what should $y and $z be?
-        assume ($y == (???))
-        assume ($z == (???))
+        test that ($y == (???))
+        test that ($z == (???))
     
     lesson "Failure and Recovery":
         $what_happened = "nothing"
@@ -174,7 +199,7 @@ $lessons = [
             $what_happened = "success"
         
         # What do you think happened?
-        assume ($what_happened == (???))
+        test that ($what_happened == (???))
         
         # Note: a 'try' block will silence failures, so this has no effect:
         try: fail
@@ -182,11 +207,11 @@ $lessons = [
     lesson "Indexing":
         # Nomsu uses the "." operator to access things inside an object:
         $dictionary = {.dog = "A lovable doofus", .cat = "An internet superstar"}
-        assume ($dictionary.dog == "A lovable doofus")
-        assume ($dictionary.cat == (???))
+        test that ($dictionary.dog == "A lovable doofus")
+        test that ($dictionary.cat == (???))
         
         # If you try to access a key that's not in an object, the result is (nil):
-        assume ($dictionary.mimsy == (???))
+        test that ($dictionary.mimsy == (???))
         
         # $dictionary.dog is just a shorthand for $dictionary."dog".
             You may need to use the longer form for strings with spaces:
@@ -197,22 +222,22 @@ $lessons = [
         $dictionary.5 = "The number five"
         $dictionary.five = 5
         $dictionary.myself = $dictionary
-        assume ($dictionary.myself == (???))
+        test that ($dictionary.myself == (???))
         
         # Lists are similar, but use square brackets ([])
             and can only have numbers as keys, starting at 1:
         $list = ["first", "second", 999]
-        assume ($list.1 == "first")
-        assume ($list.2 == (???))
-        assume ($list.3 == (???))
+        test that ($list.1 == "first")
+        test that ($list.2 == (???))
+        test that ($list.3 == (???))
         
         # Hint: 4 should be a missing key
-        assume ($list.4 == (???))
-        assume ($list.foobar == (???))
+        test that ($list.4 == (???))
+        test that ($list.foobar == (???))
         
         # The "#" action gets the number of items inside something:
-        assume ((#$list) == (???))
-        assume ((#{.x = 10, .y = 20}) == (???))
+        test that ((#$list) == (???))
+        test that ((#{.x = 10, .y = 20}) == (???))
     
     lesson "Methods":
         # The "," is used for method calls, which means calling an action
@@ -220,17 +245,17 @@ $lessons = [
         # Lists have an "add" method that puts new items at the end:
         $list = [-4, -6, 5]
         $list, add 3
-        assume ($list == [-4, -6, 5, 3])
+        test that ($list == [-4, -6, 5, 3])
         $list, add 7
-        assume ($list == [???])
+        test that ($list == [???])
         
         # Text also has some methods like:
         $name = "Harry Tuttle"
-        assume (($name, character 7) == "T")
-        assume (($name, with "Tuttle" -> "Buttle") == (???))
+        test that (($name, from 7 to 12) == "Tuttle")
+        test that (($name, with "Tuttle" -> "Buttle") == (???))
         
         # Methods can be chained too:
-        assume (($name, with "Tuttle" -> "Buttle", character 7) == (???))
+        test that (($name, with "Tuttle" -> "Buttle", from 7 to 12) == (???))
     
     lesson "Object Oriented Programming":
         # Object Oriented Programming deals with things that have
@@ -246,13 +271,30 @@ $lessons = [
             ($self, add $bit) means:
                 $bits, add $bit
             
-            # Write a method called ($self, length) that returns the total
-                length of all the bits in the buffer:
+            # Write a method called ($self, length) that returns the sum
+                of the lengths of each bit in the buffer:
             <your code here>
         $b = (a Buffer)
         $b, add "xx"
         $b, add "yyy"
-        assume (($b, length) == 5)
+        test that (($b, length) == 5)
+
+    lesson "Files Part 1":
+        # Define an external action here:
+        external:
+            # These will be used in the next lesson
+            $foobar = 23
+            ($x tripled) means:
+                <your code here>
+        test that ((5 tripled) == 15)
+        test that ((2 tripled) == 6)
+
+    lesson "Files Part 2":
+        # 'use' is the action for importing from other files
+        # It takes the path to the file (without the .nom extension):
+        use (<prev lesson>)
+        test that ((10 tripled) == (???))
+        test that ($foobar == (???))
 ]
 
 $(ask normally) = $(ask)
@@ -282,14 +324,12 @@ command line program with $args:
         unless ($Files.exists $tutorial_dir):
             when
                 ask ("
-                    The Nomsu tutorial files will be in \$tutorial_dir is that okay? [Y/n] \;
+                    The Nomsu tutorial files will be in \$tutorial_dir is that okay? [Y/n/exit] \;
                 ")
             ..is:
                 "n" "N" "no":
-                    say ("
-                        Okay. If you want to specify another file location, run `nomsu -t tutorial <your location>`
-                    ")
-                    exit
+                    $tutorial_dir = (ask "Where do you want to put the tutorial? ")
+                "exit" "quit" "q" "e": exit
     ..else:
         $tutorial_dir = $args.extras.1
     
@@ -300,7 +340,10 @@ command line program with $args:
     for $lesson in $lessons at $i:
         $filename = (filename of $i)
         unless ($Files.exists $filename):
-            write $lesson.lesson to file $filename
+            $lesson_text =
+                $lesson.lesson, with "%(<prev lesson>%)" ->
+                    "\"\(filename of ($i - 1), with "%.nom$" -> "", with "^%./" -> "")\""
+            write $lesson_text to file $filename
     
     # Display info about editing the tutorial files:
     if $args.x:
@@ -328,14 +371,23 @@ command line program with $args:
                     > \;
                 ")
             if ($EDITOR == ""): $EDITOR = (nil)
+
+    (run lesson $i) means:
+        $filename = (filename of $i)
+        $file = (read file $filename)
+        $file = ($NomsuCode, from (Source $filename 1 (#$file)) $file)
+        $tree = ($file parsed)
+        $tree =
+            $tree with $ ->:
+                if ($ == \(<prev lesson>)):
+                    return ("Text" tree with (filename of ($i - 1), with "%.nom$" -> ""))
+        run $tree
+
     
     (get failures) means [
         : for $lesson in $lessons at $i:
-            $filename = (filename of $i)
-            $file = (read file $filename)
-            $file = ($NomsuCode, from (Source $filename 1 (#$file)) $file)
             try:
-                run $file
+                run lesson $i
             ..if it fails with $msg:
                 $msg = ($msg, with "\n *stack traceback:.*" -> "")
                 add {.lesson_number = $i, .failure = $msg}
@@ -360,17 +412,21 @@ command line program with $args:
     for $lesson in $lessons at $i:
         for $f in $failures:
             if ($f.lesson_number == $i):
-                say (bold (red "    \$i. \($lesson.name) [incomplete]"))
+                say "\(red "  - ")\(bold (red "\$i. \($lesson.name) [incomplete]"))"
                 do next $lesson
-        say (bold (green "    \$i. \($lesson.name) [passed]"))
+        say "\(green "  + ")\(bold (green "\$i. \($lesson.name) [passed]"))"
     
-    say ("
+    if $(COLOR ENABLED):
+        say ("
+            
+            \(bold "Your progress:") \(
+                20 wide (((#$lessons) - (#$failures)) / (#$lessons)) progress bar
+            )
+        ")
+    ..else:
+        say
+        say (((#$lessons) - (#$failures)) / (#$lessons) progress bar)
         
-        \(bold "Your progress:") \(
-            20 wide (((#$lessons) - (#$failures)) / (#$lessons)) progress bar
-        )
-    ")
-    
     repeat until ($failures is empty):
         show first failure from $failures
         
@@ -400,6 +456,8 @@ command line program with $args:
             --- (retry file) ---
             when (ask "Edit \$filename to get it to pass? [Y/n/exit] ") is:
                 "q" "quit" "exit" "n" "N" "no": exit
+                "c":
+                    write "# cheater!\n" to file $filename
                 "y" "Y" "yes" "":
                     $f = (read file $filename)
                     [$line, $col] = ($failures.1.failure, match ":(%d+),(%d+)")
@@ -422,10 +480,8 @@ command line program with $args:
                 else:
                     say "Sorry, I don't understand that."
                     go to (retry file)
-            $file = (read file $filename)
-            $file = ($NomsuCode, from (Source $filename 1 (#$file)) $file)
             try:
-                run $file
+                run lesson $failures.1.lesson_number
             ..if it fails with $msg:
                 $failures.1.failure = $msg
                 say (bold (red "\n There's a bit more to fix:"))
@@ -443,13 +499,16 @@ command line program with $args:
                 say (bold (green "\nSuccess!\n"))
             ..else:
                 say (bold (red "\nUh oh, that broke something.\n"))
-            $N = 100
-            for $ in 0 to $N:
-                $k = (($ / $N) smoothed by 2)
-                $p = ($prev_progress to $progress mixed by $k)
-                say "\r\(bold "Your progress:") \(20 wide $p progress bar)" inline
-                $io.flush()
-                sleep for (1 / $N) seconds
+            if $(COLOR ENABLED):
+                $N = 100
+                for $ in 0 to $N:
+                    $k = (($ / $N) smoothed by 2)
+                    $p = ($prev_progress to $progress mixed by $k)
+                    say "\r\(bold "Your progress:") \(20 wide $p progress bar)" inline
+                    $io.flush()
+                    sleep for (1 / $N) seconds
+            ..else:
+                say (((#$lessons) - (#$failures)) / (#$lessons) progress bar)
             say
     
     # All done, no more failures:
@@ -459,7 +518,7 @@ command line program with $args:
         
                You've passed the tutorial!
         
-                        \\(^ᴗ^)/
+                        \\(^\("ᴗ" if $(COLOR ENABLED) else "_")^)/
         
         
     ")
diff --git a/nomsu.lua b/nomsu.lua
index dc5b97f..21e4af2 100644
--- a/nomsu.lua
+++ b/nomsu.lua
@@ -1,16 +1,17 @@
 local clibtype = package.cpath:match("?%.(so)") or package.cpath:match("?%.(dll)")
+COLOR_ENABLED = true
 if clibtype == "dll" then
+  local enable_colors = require('wincolors')
+  local ok, _ = pcall(enable_colors)
+  if not ok then
+    COLOR_ENABLED = false
+  end
   os.execute("chcp 65001>nul")
 end
 if NOMSU_VERSION and NOMSU_PREFIX then
   package.path = tostring(NOMSU_PREFIX) .. "/share/nomsu/" .. tostring(NOMSU_VERSION) .. "/?.lua;" .. package.path
   package.cpath = tostring(NOMSU_PREFIX) .. "/lib/nomsu/" .. tostring(NOMSU_VERSION) .. "/?." .. tostring(clibtype) .. ";" .. package.cpath
 end
-local EXIT_SUCCESS, EXIT_FAILURE = 0, 1
-if _VERSION == "Lua 5.1" and not jit then
-  print("Sorry, Nomsu does not run on Lua 5.1. Please use LuaJIT 2+ or Lua 5.2+")
-  os.exit(EXIT_FAILURE)
-end
 local usage = [=[Nomsu Compiler
 
 Usage: (nomsu | lua nomsu.lua | moon nomsu.moon) [-V version] [--help | -h] [--version] [-O optimization level] [-v] [-c] [-s] [-d debugger] [--no-core] [(file | -t tool | -e "nomsu code..." | files... -- ) [nomsu args...]]
@@ -92,7 +93,7 @@ local arg_string = table.concat(arg, sep) .. sep
 local args, err = parser:match(arg_string)
 if not args or err or args.help then
   if err then
-    print("Didn't understand: \x1b[31;1m" .. tostring(err) .. "\x1b[0m")
+    print("Didn't understand: " .. tostring(err))
   end
   print(usage)
   os.exit(EXIT_FAILURE)
@@ -142,6 +143,7 @@ nomsu_environment.COMMAND_LINE_ARGS = nomsu_args
 nomsu_environment.OPTIMIZATION = optimization
 nomsu_environment.NOMSU_PACKAGEPATH = NOMSU_PACKAGEPATH
 nomsu_environment.NOMSU_PREFIX = NOMSU_PREFIX
+nomsu_environment.COLOR_ENABLED = COLOR_ENABLED
 local run
 run = function()
   if not (args.no_core) then
diff --git a/nomsu.moon b/nomsu.moon
index 240d457..96053eb 100755
--- a/nomsu.moon
+++ b/nomsu.moon
@@ -2,7 +2,14 @@
 -- This file contains the command-line Nomsu runner.
 
 clibtype = package.cpath\match("?%.(so)") or package.cpath\match("?%.(dll)")
+export COLOR_ENABLED
+COLOR_ENABLED = true
 if clibtype == "dll"
+    -- Enable colors:
+    enable_colors = require('wincolors')
+    ok,_ = pcall(enable_colors)
+    if not ok
+        COLOR_ENABLED = false
     -- Special hack to enable utf8 for windows console applications:
     os.execute("chcp 65001>nul")
 
@@ -10,13 +17,6 @@ if NOMSU_VERSION and NOMSU_PREFIX
     package.path = "#{NOMSU_PREFIX}/share/nomsu/#{NOMSU_VERSION}/?.lua;"..package.path
     package.cpath = "#{NOMSU_PREFIX}/lib/nomsu/#{NOMSU_VERSION}/?.#{clibtype};"..package.cpath
 
-EXIT_SUCCESS, EXIT_FAILURE = 0, 1
-
-if _VERSION == "Lua 5.1" and not jit
-    -- Cannot run on Lua5.1 because it doesn't have gotos.
-    print("Sorry, Nomsu does not run on Lua 5.1. Please use LuaJIT 2+ or Lua 5.2+")
-    os.exit(EXIT_FAILURE)
-
 usage = [=[
 Nomsu Compiler
 
@@ -91,7 +91,7 @@ arg_string = table.concat(arg, sep)..sep
 args, err = parser\match(arg_string)
 if not args or err or args.help
     if err
-        print("Didn't understand: \x1b[31;1m#{err}\x1b[0m")
+        print("Didn't understand: #{err}")
     print usage
     os.exit(EXIT_FAILURE)
 nomsu_args = Dict{}
@@ -121,6 +121,7 @@ nomsu_environment.COMMAND_LINE_ARGS = nomsu_args
 nomsu_environment.OPTIMIZATION = optimization
 nomsu_environment.NOMSU_PACKAGEPATH = NOMSU_PACKAGEPATH
 nomsu_environment.NOMSU_PREFIX = NOMSU_PREFIX
+nomsu_environment.COLOR_ENABLED = COLOR_ENABLED
 
 run = ->
     unless args.no_core
diff --git a/nomsu_compiler.lua b/nomsu_compiler.lua
index 0cedd50..c9a15db 100644
--- a/nomsu_compiler.lua
+++ b/nomsu_compiler.lua
@@ -9,6 +9,7 @@ do
   local _obj_0 = require("code_obj")
   LuaCode, Source = _obj_0.LuaCode, _obj_0.Source
 end
+require("text")
 local SyntaxTree = require("syntax_tree")
 local Files = require("files")
 local pretty_error = require("pretty_errors")
@@ -20,6 +21,17 @@ fail_at = function(source, msg)
     source = source.source
   elseif type(source) == 'string' then
     source = Source:from_string(source)
+  else
+    assert(source.short_src and source.currentline)
+    file = Files.read(source.short_src)
+    assert(file, "Could not find " .. tostring(source.short_src))
+    local lines = file:lines()
+    local start = 1
+    for i = 1, source.currentline - 1 do
+      start = start + #lines[i]
+    end
+    local stop = start + #lines[source.currentline]
+    source = Source(source.short_src, start, stop)
   end
   if source and not file then
     file = Files.read(source.filename)
diff --git a/nomsu_compiler.moon b/nomsu_compiler.moon
index 3993490..73cc5a8 100644
--- a/nomsu_compiler.moon
+++ b/nomsu_compiler.moon
@@ -4,6 +4,7 @@
 unpack or= table.unpack
 {:match, :sub, :gsub, :format, :byte, :find} = string
 {:LuaCode, :Source} = require "code_obj"
+require "text"
 SyntaxTree = require "syntax_tree"
 Files = require "files"
 
@@ -15,6 +16,18 @@ fail_at = (source, msg)->
         source = source.source
     elseif type(source) == 'string'
         source = Source\from_string(source)
+    else
+        -- debug.getinfo() output:
+        assert(source.short_src and source.currentline)
+        file = Files.read(source.short_src)
+        assert file, "Could not find #{source.short_src}"
+        lines = file\lines!
+        start = 1
+        for i=1,source.currentline-1
+            start += #lines[i]
+        stop = start + #lines[source.currentline]
+        source = Source(source.short_src, start, stop)
+
     if source and not file
         file = Files.read(source.filename)
 
diff --git a/nomsu_environment.lua b/nomsu_environment.lua
index e359257..5ea6a62 100644
--- a/nomsu_environment.lua
+++ b/nomsu_environment.lua
@@ -12,6 +12,7 @@ local Text = require('text')
 local SyntaxTree = require("syntax_tree")
 local Files = require("files")
 local Errhand = require("error_handling")
+local C = require("colors")
 local make_parser = require("parser")
 local pretty_error = require("pretty_errors")
 local make_tree
@@ -65,7 +66,6 @@ do
   local _obj_0 = require('nomsu_compiler')
   compile, fail_at = _obj_0.compile, _obj_0.fail_at
 end
-local _currently_running_files = List({ })
 local _module_imports = { }
 local _importer_mt = {
   __index = function(self, k)
@@ -225,7 +225,7 @@ nomsu_environment = Importer({
         err_strings = _accum_0
       end
       if num_errs > #err_strings then
-        table.insert(err_strings, "\027[31;1m +" .. tostring(num_errs - #err_strings) .. " additional errors...\027[0m\n")
+        table.insert(err_strings, C("bright red", " +" .. tostring(num_errs - #err_strings) .. " additional errors...\n"))
       end
       error(table.concat(err_strings, '\n\n'), 0)
     end
@@ -249,11 +249,27 @@ nomsu_environment = Importer({
         return ret
       end
     end
-    if _currently_running_files:has(path) then
-      local i = _currently_running_files:index_of(path)
-      _currently_running_files:add(path)
-      local circle = _currently_running_files:from_1_to(i, -1)
-      error("Circular import detected:\n           " .. circle:joined_with("\n..imports  "))
+    local currently_running = { }
+    for i = 2, 999 do
+      local info = debug.getinfo(i, 'f')
+      if not (info.func) then
+        break
+      end
+      if info.func == self.Module then
+        local n, upper_path = debug.getlocal(i, 3)
+        table.insert(currently_running, upper_path)
+        assert(n == "path")
+        if upper_path == path then
+          local circle = table.concat(currently_running, "', which imports '")
+          local err_i = 2
+          info = debug.getinfo(err_i)
+          while info and (info.func == self.Module or info.func == self.use or info.func == self.export) do
+            err_i = err_i + 1
+            info = debug.getinfo(err_i)
+          end
+          fail_at((info or debug.getinfo(2)), "Circular import: File '" .. tostring(path) .. "' imports '" .. circle .. "'")
+        end
+      end
     end
     local mod = self:new_environment()
     mod.MODULE_NAME = package_name
@@ -263,12 +279,10 @@ nomsu_environment = Importer({
     else
       code = NomsuCode:from(Source(path, 1, #code), code)
     end
-    _currently_running_files:add(path)
     local ret = mod:run(code)
     if ret ~= nil then
       mod = ret
     end
-    _currently_running_files:pop()
     package.nomsuloaded[package_name] = mod
     package.nomsuloaded[path] = mod
     return mod
@@ -360,7 +374,7 @@ nomsu_environment = Importer({
           lines = _accum_0
         end
         local line_numbered_lua = table.concat(lines, "\n")
-        error("Failed to compile generated code:\n\027[1;34m" .. tostring(line_numbered_lua) .. "\027[0m\n\n" .. tostring(err), 0)
+        error("Failed to compile generated code:\n" .. tostring(C("bright blue", line_numbered_lua)) .. "\n\n" .. tostring(err), 0)
       end
       local source_key = tostring(source)
       if not (self.SOURCE_MAP[source_key] or self.OPTIMIZATION >= 2) then
diff --git a/nomsu_environment.moon b/nomsu_environment.moon
index 1deac6f..d572f8c 100644
--- a/nomsu_environment.moon
+++ b/nomsu_environment.moon
@@ -6,6 +6,7 @@ Text = require 'text'
 SyntaxTree = require "syntax_tree"
 Files = require "files"
 Errhand = require "error_handling"
+C = require "colors"
 make_parser = require("parser")
 pretty_error = require("pretty_errors")
 
@@ -35,7 +36,6 @@ for version=1,999
 
 {:tree_to_nomsu, :tree_to_inline_nomsu} = require "nomsu_decompiler"
 {:compile, :fail_at} = require('nomsu_compiler')
-_currently_running_files = List{} -- Used to check for circular imports in run_file_1_in
 _module_imports = {}
 _importer_mt = {__index: (k)=> _module_imports[@][k]}
 Importer = (t, imports)->
@@ -108,12 +108,13 @@ nomsu_environment = Importer{
                     start:e.source.start, stop:e.source.stop, filename:e.source.filename
                 } for i, e in ipairs(errs) when i <= 3]
             if num_errs > #err_strings
-                table.insert(err_strings, "\027[31;1m +#{num_errs-#err_strings} additional errors...\027[0m\n")
+                table.insert(err_strings, C("bright red", " +#{num_errs-#err_strings} additional errors...\n"))
             error(table.concat(err_strings, '\n\n'), 0)
         
         return tree
 
     Module: (package_name)=>
+        -- This *must* be the first local
         local path
         if package_name\match("%.nom$") or package_name\match("%.lua")
             path = package_name
@@ -125,11 +126,26 @@ nomsu_environment = Importer{
         if ret = package.nomsuloaded[package_name] or package.nomsuloaded[path]
             return ret
 
-        if _currently_running_files\has(path)
-            i = _currently_running_files\index_of(path)
-            _currently_running_files\add path
-            circle = _currently_running_files\from_1_to(i, -1)
-            error("Circular import detected:\n           "..circle\joined_with("\n..imports  "))
+        -- Traverse up the callstack to look for import loops
+        -- This is more reliable than keeping a list of running files, since
+        -- that gets messed up when errors occur.
+        currently_running = {}
+        for i=2,999
+            info = debug.getinfo(i, 'f')
+            break unless info.func
+            if info.func == @Module
+                n, upper_path = debug.getlocal(i, 3) -- 3 means "path"
+                table.insert(currently_running, upper_path)
+                assert(n == "path")
+                if upper_path == path
+                    --circle = "\n           "..table.concat(currently_running, "\n..imports  ")
+                    circle = table.concat(currently_running, "', which imports '")
+                    err_i = 2
+                    info = debug.getinfo(err_i)
+                    while info and (info.func == @Module or info.func == @use or info.func == @export)
+                        err_i += 1
+                        info = debug.getinfo(err_i)
+                    fail_at (info or debug.getinfo(2)), "Circular import: File '#{path}' imports '"..circle.."'"
         mod = @new_environment!
         mod.MODULE_NAME = package_name
         code = Files.read(path)
@@ -137,11 +153,9 @@ nomsu_environment = Importer{
             code = LuaCode\from(Source(path, 1, #code), code)
         else
             code = NomsuCode\from(Source(path, 1, #code), code)
-        _currently_running_files\add path
         ret = mod\run(code)
         if ret != nil
             mod = ret
-        _currently_running_files\pop!
         package.nomsuloaded[package_name] = mod
         package.nomsuloaded[path] = mod
         return mod
@@ -165,7 +179,6 @@ nomsu_environment = Importer{
                 imports[k] = v
         for k,v in pairs(mod)
             if rawget(@, k) == nil
-                --if k != "_G" and k != "_ENV" and k != "COMPILE_RULES" and k != "MODULE_NAME"
                 @[k] = v
         cr_imports = assert _module_imports[@COMPILE_RULES]
         if mod.COMPILE_RULES
@@ -210,7 +223,7 @@ nomsu_environment = Importer{
             if not run_lua_fn
                 lines =[("%3d|%s")\format(i,line) for i, line in ipairs lua_string\lines!]
                 line_numbered_lua = table.concat(lines, "\n")
-                error("Failed to compile generated code:\n\027[1;34m#{line_numbered_lua}\027[0m\n\n#{err}", 0)
+                error("Failed to compile generated code:\n#{C("bright blue", line_numbered_lua)}\n\n#{err}", 0)
             source_key = tostring(source)
             unless @SOURCE_MAP[source_key] or @OPTIMIZATION >= 2
                 map = {}
diff --git a/pretty_errors.lua b/pretty_errors.lua
index ecc6cd2..a675f12 100644
--- a/pretty_errors.lua
+++ b/pretty_errors.lua
@@ -1,5 +1,6 @@
 require("containers")
 local Text = require('text')
+local C = require('colors')
 local box
 box = function(text)
   local max_line = 0
@@ -8,7 +9,7 @@ box = function(text)
   end
   local ret = ("\n" .. text):gsub("\n([^\n]*)", function(line)
     local line_len = #(line:gsub("\027%[[0-9;]*m", ""))
-    return "\n" .. tostring(line) .. tostring((" "):rep(max_line - line_len)) .. " \027[0m"
+    return "\n" .. tostring(line) .. tostring((" "):rep(max_line - line_len)) .. " " .. C('reset')
   end)
   return ret:sub(2, -1), max_line
 end
@@ -20,13 +21,16 @@ format_error = function(err)
   local nl_indicator = (err_linepos > #err_line) and " " or ""
   local fmt_str = " %" .. tostring(#tostring(err_linenum + context)) .. "d|"
   local pointer = (" "):rep(err_linepos + #fmt_str:format(0) - 1) .. ("^"):rep(err_size)
-  local err_msg = "\027[31;1m" .. tostring(err.title or "Error") .. " at " .. tostring(err.filename or '???') .. ":" .. tostring(err_linenum) .. "," .. tostring(err_linepos) .. "\027[0m"
+  local err_msg = C('bold red', err.title or "Error") .. C('red', " at " .. tostring(err.filename or '???') .. ":" .. tostring(err_linenum) .. "," .. tostring(err_linepos))
+  if not (COLOR_ENABLED) then
+    err_msg = err_msg .. "\n"
+  end
   local lines = err.source:lines()
   for i = err_linenum - context, err_linenum - 1 do
     do
       local line = lines[i]
       if line then
-        err_msg = err_msg .. "\n\027[2m" .. tostring(fmt_str:format(i)) .. "\027[0m" .. tostring(line) .. "\027[0m"
+        err_msg = err_msg .. ("\n" .. C('dim', fmt_str:format(i)) .. line)
       end
     end
   end
@@ -34,8 +38,8 @@ format_error = function(err)
     local before = err_line:sub(1, err_linepos - 1)
     local during = err_line:sub(err_linepos, err_linepos + err_size - 1)
     local after = err_line:sub(err_linepos + err_size, -1)
-    err_line = "\027[0m" .. tostring(before) .. "\027[41;30m" .. tostring(during) .. tostring(nl_indicator) .. "\027[0m" .. tostring(after)
-    err_msg = err_msg .. "\n\027[2m" .. tostring(fmt_str:format(err_linenum)) .. tostring(err_line) .. "\027[0m"
+    err_line = before .. C('black on red', during .. nl_indicator) .. after
+    err_msg = err_msg .. ("\n" .. C('dim', fmt_str:format(err_linenum)) .. err_line)
   end
   local _, err_linenum_end, err_linepos_end = err.source:line_info_at(err.stop)
   err_linenum_end = err_linenum_end or err_linenum
@@ -48,9 +52,9 @@ format_error = function(err)
         if line then
           if i == err_linenum_end then
             local during, after = line:sub(1, err_linepos_end - 1), line:sub(err_linepos_end, -1)
-            err_msg = err_msg .. "\n\027[2m" .. tostring(fmt_str:format(i)) .. "\027[0;41;30m" .. tostring(during) .. "\027[0m" .. tostring(after)
+            err_msg = err_msg .. ("\n" .. C('dim', fmt_str:format(i)) .. C('black on red', during) .. after)
           else
-            err_msg = err_msg .. "\n\027[2m" .. tostring(fmt_str:format(i)) .. "\027[0;41;30m" .. tostring(line) .. "\027[0m"
+            err_msg = err_msg .. ("\n" .. C('dim', fmt_str:format(i)) .. C('black on red', line))
           end
         end
       end
@@ -61,19 +65,25 @@ format_error = function(err)
     end
   end
   local box_width = 70
-  local err_text = "\027[47;30;1m" .. tostring(" " .. err.error:wrapped_to(box_width, 16):gsub("\n", "\n\027[47;30;1m "))
+  local err_text = C('black on white', " " .. err.error:wrapped_to(box_width, 16):gsub("\n", "\n" .. C('black on white') .. " "))
   if err.hint then
-    err_text = err_text .. "\n\027[47;30;3m" .. tostring((" Suggestion: " .. tostring(err.hint)):wrapped_to(box_width, 16):gsub("\n", "\n\027[47;30;3m "))
+    err_text = err_text .. ("\n" .. C('italic black on white', (" Suggestion: " .. tostring(err.hint)):wrapped_to(box_width, 16):gsub("\n", "\n" .. C('italic black on white') .. " ")))
+  end
+  err_msg = err_msg .. ("\n " .. box(err_text):gsub("\n", "\n "))
+  if not (COLOR_ENABLED) then
+    err_msg = err_msg .. "\n"
   end
-  err_msg = err_msg .. ("\n\027[33;1m " .. box(err_text):gsub("\n", "\n "))
   for i = err_linenum_end + 1, err_linenum_end + context do
     do
       local line = lines[i]
       if line then
-        err_msg = err_msg .. "\n\027[2m" .. tostring(fmt_str:format(i)) .. "\027[0m" .. tostring(line) .. "\027[0m"
+        err_msg = err_msg .. ("\n" .. C('dim', fmt_str:format(i)) .. line)
       end
     end
   end
+  if not (COLOR_ENABLED) then
+    err_msg = err_msg .. "\n"
+  end
   return err_msg
 end
 return format_error
diff --git a/pretty_errors.moon b/pretty_errors.moon
index bb8f63f..b769d32 100644
--- a/pretty_errors.moon
+++ b/pretty_errors.moon
@@ -2,6 +2,7 @@
 -- line numbers, code excerpts, and so on.
 require "containers"
 Text = require 'text'
+C = require 'colors'
 
 box = (text)->
     max_line = 0
@@ -9,7 +10,7 @@ box = (text)->
         max_line = math.max(max_line, #(line\gsub("\027%[[0-9;]*m","")))
     ret = ("\n"..text)\gsub "\n([^\n]*)", (line)->
         line_len = #(line\gsub("\027%[[0-9;]*m",""))
-        return "\n#{line}#{(" ")\rep(max_line-line_len)} \027[0m"
+        return "\n#{line}#{(" ")\rep(max_line-line_len)} "..C('reset')
     return ret\sub(2,-1), max_line
 
 format_error = (err)->
@@ -26,17 +27,18 @@ format_error = (err)->
     --else
     --    (" ")\rep(err_linepos+#fmt_str\format(0)-1).."⬆"
 
-    err_msg = "\027[31;1m#{err.title or "Error"} at #{err.filename or '???'}:#{err_linenum},#{err_linepos}\027[0m"
+    err_msg = C('bold red', err.title or "Error")..C('red', " at #{err.filename or '???'}:#{err_linenum},#{err_linepos}")
+    err_msg ..= "\n" unless COLOR_ENABLED
     lines = err.source\lines!
     for i=err_linenum-context,err_linenum-1
         if line = lines[i]
-            err_msg ..= "\n\027[2m#{fmt_str\format(i)}\027[0m#{line}\027[0m"
+            err_msg ..= "\n"..C('dim', fmt_str\format(i))..line
     if err_line
         before = err_line\sub(1, err_linepos-1)
         during = err_line\sub(err_linepos,err_linepos+err_size-1)
         after = err_line\sub(err_linepos+err_size, -1)
-        err_line = "\027[0m#{before}\027[41;30m#{during}#{nl_indicator}\027[0m#{after}"
-        err_msg ..= "\n\027[2m#{fmt_str\format(err_linenum)}#{err_line}\027[0m"
+        err_line = before..C('black on red', during..nl_indicator)..after
+        err_msg ..= "\n"..C('dim', fmt_str\format(err_linenum))..err_line
     _, err_linenum_end, err_linepos_end = err.source\line_info_at(err.stop)
     err_linenum_end or= err_linenum
     if err_linenum_end == err_linenum
@@ -46,22 +48,24 @@ format_error = (err)->
             if line = lines[i]
                 if i == err_linenum_end
                     during, after = line\sub(1,err_linepos_end-1), line\sub(err_linepos_end,-1)
-                    err_msg ..= "\n\027[2m#{fmt_str\format(i)}\027[0;41;30m#{during}\027[0m#{after}"
+                    err_msg ..= "\n"..C('dim', fmt_str\format(i))..C('black on red', during)..after
                 else
-                    err_msg ..= "\n\027[2m#{fmt_str\format(i)}\027[0;41;30m#{line}\027[0m"
+                    err_msg ..= "\n"..C('dim', fmt_str\format(i))..C('black on red', line)
             if i > err_linenum+1 + 5
                 err_msg ..= "\n       ...\n"
                 break
 
     box_width = 70
-    err_text = "\027[47;30;1m#{" "..err.error\wrapped_to(box_width, 16)\gsub("\n", "\n\027[47;30;1m ")}"
+    err_text = C('black on white', " "..err.error\wrapped_to(box_width, 16)\gsub("\n", "\n"..C('black on white').." "))
     if err.hint
-        err_text ..= "\n\027[47;30;3m#{(" Suggestion: #{err.hint}")\wrapped_to(box_width, 16)\gsub("\n", "\n\027[47;30;3m ")}"
-    err_msg ..= "\n\027[33;1m "..box(err_text)\gsub("\n", "\n ")
+        err_text ..= "\n"..C('italic black on white', (" Suggestion: #{err.hint}")\wrapped_to(box_width, 16)\gsub("\n", "\n"..C('italic black on white').." "))
+    err_msg ..= "\n "..box(err_text)\gsub("\n", "\n ")
+    err_msg ..= "\n" unless COLOR_ENABLED
 
     for i=err_linenum_end+1,err_linenum_end+context
         if line = lines[i]
-            err_msg ..= "\n\027[2m#{fmt_str\format(i)}\027[0m#{line}\027[0m"
+            err_msg ..= "\n"..C('dim', fmt_str\format(i))..line
+    err_msg ..= "\n" unless COLOR_ENABLED
     return err_msg
 
 return format_error