diff --git a/takawiri.retro b/takawiri.retro
index 47d3619..6f99c17 100755
--- a/takawiri.retro
+++ b/takawiri.retro
@@ -18,14 +18,18 @@ Setup the text output buffer dimensions.
 #25 'TOB:H const
 ~~~
 
-Setup the local terminal dimensions.
-
-TODO: some systems may provide this in the environment. See if
-      this can be pulled in automatically if present?
+Setup the local terminal dimensions. This requires the current
+development build of Retro to gain access to the `ioctl:` words.
+(If not using this, hard code the terminal constraints for your
+system).
 
 ~~~
-#105 'LT:W const
-#30  'LT:H const
+ioctl:term-size (rows,cols) 'LT:W const 'LT:H const
+~~~
+
+~~~
+LT:W #100 lt? [ 'Terminal_too_narrow! s:put nl bye ] if
+LT:H #27 lt?  [ 'Terminal_too_short! s:put nl bye ] if
 ~~~
 
 # Dependencies