diff --git a/src/apis/unicode.lua b/src/apis/unicode.lua
index 2f16edb..0ca88b8 100644
--- a/src/apis/unicode.lua
+++ b/src/apis/unicode.lua
@@ -3,21 +3,24 @@ local env = ...
 local utf8 = require("utf8")
 
 env.unicode = {
-	lower = utf8.lower,
-	upper = utf8.upper,
 	char = utf8.char,
 	len = utf8.len,
 	reverse = utf8.reverse,
 	sub = utf8.sub,
 }
 
-local function getCharWidth(char)
-	if unifont[char] ~= nil then
-		return #unifont[char] / 32
-	end
-	return 1
+function env.unicode.lower(str)
+	cprint("unicode.lower", str)
+	if type(str) == "number" then str = tostring(str) end
+	checkArg(1,str,"string")
+	return utf8.lower(str)
+end
+function env.unicode.upper(str)
+	cprint("unicode.upper", str)
+	if type(str) == "number" then str = tostring(str) end
+	checkArg(1,str,"string")
+	return utf8.upper(str)
 end
-
 function env.unicode.isWide(str)
 	cprint("unicode.isWide", str)
 	checkArg(1,str,"string")
diff --git a/src/component/screen_sdl2.lua b/src/component/screen_sdl2.lua
index 67d7461..742aa7e 100644
--- a/src/component/screen_sdl2.lua
+++ b/src/component/screen_sdl2.lua
@@ -111,8 +111,8 @@ function elsa.draw()
 	SDL.renderPresent(renderer)
 end
 
-local char8 = ffi.new("uint32_t[?]", 8*16);
-local char16 = ffi.new("uint32_t[?]", 16*16);
+local char8 = ffi.new("uint32_t[?]", 8*16)
+local char16 = ffi.new("uint32_t[?]", 16*16)
 local function renderChar(char,x,y,fg,bg)
 	if unifont[char] == nil then
 		char = 63
@@ -139,15 +139,31 @@ local function renderChar(char,x,y,fg,bg)
 	SDL.updateTexture(texture, ffi.new("SDL_Rect",{x=x,y=y,w=size*4,h=16}), pchar, (size*4) * ffi.sizeof("uint32_t"))
 end
 
-local function setPos(x,y,c,fg,bg)
-	local renderchange = screen.txt[y][x] ~= utf8.char(c) or screen.bg[y][x] ~= scrbgc or (screen.txt[y][x] ~= " " and screen.fg[y][x] ~= scrfgc)
+local function screenSet(x,y,c)
 	screen.txt[y][x] = utf8.char(c)
 	screen.fg[y][x] = scrfgc
 	screen.bg[y][x] = scrbgc
 	screen.fgp[y][x] = scrfgp
 	screen.bgp[y][x] = scrbgp
+end
+
+local function setPos(x,y,c,fg,bg)
+	local renderchange = screen.txt[y][x] ~= utf8.char(c) or screen.bg[y][x] ~= scrbgc or (screen.txt[y][x] ~= " " and screen.fg[y][x] ~= scrfgc)
+	local charWidth = getCharWidth(c)
+	local renderafter = getCharWidth(utf8.byte(screen.txt[y][x])) > 1 and charWidth == 1 and x < width
+	if x > 1 and getCharWidth(utf8.byte(screen.txt[y][x-1])) > 1 then
+		renderchange = false
+	else
+		screenSet(x,y,c)
+	end
 	if renderchange then
 		renderChar(c,(x-1)*8,(y-1)*16,fg,bg)
+		if charWidth > 1 and x < width then
+			screenSet(x+1,y,32)
+		end
+	end
+	if renderafter then
+		renderChar(32,x*8,(y-1)*16,screen.fg[y][x+1],screen.bg[y][x+1])
 	end
 end
 
@@ -248,14 +264,14 @@ function cec.fill(x1, y1, w, h, char) -- Fills a portion of the screen at the sp
 	if w <= 0 or h <= 0 then
 		return true
 	end
-	local x2 = x1+w-1
+	local code = utf8.byte(char)
+	local x2 = x1+(w*getCharWidth(code))-1
 	local y2 = y1+h-1
 	if x2 < 1 or y2 < 1 or x1 > width or y1 > height then
 		return true
 	end
-	local code = utf8.byte(char)
 	for y = y1,y2 do
-		for x = x1,x2 do
+		for x = x1,x2,getCharWidth(code) do
 			setPos(x,y,code,scrfgc,scrbgc)
 		end
 	end
@@ -305,7 +321,7 @@ function cec.set(x, y, value, vertical) -- Plots a string value to the screen at
 			if x >= 1 then
 				setPos(x,y,c,scrfgc,scrbgc)
 			end
-			x = x + #unifont[c]/32
+			x = x + getCharWidth(c)
 			if x > width then break end
 		end
 	end
diff --git a/src/main.lua b/src/main.lua
index 340c33a..d50339a 100644
--- a/src/main.lua
+++ b/src/main.lua
@@ -45,27 +45,28 @@ machine = {
 	signals = {},
 }
 
-local function _checkArg(pos, n, have, ...)
+local function check(have, want, ...)
+	if not want then
+		return false
+	else
+		return have == want or check(have, ...)
+	end
+end
+
+function checkArg(n, have, ...)
 	have = type(have)
-	local function check(want, ...)
-		if not want then
-			return false
-		else
-			return have == want or check(...)
-		end
-	end
-	if not check(...) then
+	if not check(have, ...) then
 	    local msg = string.format("bad argument #%d (%s expected, got %s)", n, table.concat({...}, " or "), have)
-		error(msg, pos)
+		error(msg, 3)
 	end
 end
 
-function checkArg(...)
-	_checkArg(4, ...)
-end
-
-function compCheckArg(...)
-	_checkArg(5, ...)
+function compCheckArg(n, have, ...)
+	have = type(have)
+	if not check(have, ...) then
+	    local msg = string.format("bad arguments #%d (%s expected, got %s)", n, table.concat({...}, " or "), have)
+		error(msg, 4)
+	end
 end
 
 if true then
@@ -236,6 +237,12 @@ for line in elsa.filesystem.lines("unifont.hex") do
 	local a,b = line:match("(.+):(.*)")
 	unifont[tonumber(a,16)] = b
 end
+function getCharWidth(char)
+	if unifont[char] ~= nil then
+		return #unifont[char] / 32
+	end
+	return 1
+end
 
 -- load api's into environment
 elsa.filesystem.load("apis/computer.lua")(env)