• a canvas to draw on (turtle or freehand)
• buttons for reset commands, and colorful ones for setting the pen color (right-click for background color)
• a text widget that echoes commands and their results or errors, also in color
• an entry widget to type in Tcl commands with a simple history mechanism (cursor up/down moves one line; page down moves to bottom)

 proc turtleshell {} {
     wm title . Turtleshell!
     pack [entry .e -textvariable ::entrycmd] -fill x -side bottom
     bind .e <Return> {
         history:add? $entrycmd
         .t insert end $entrycmd\n blue
         set tag {}
         if [catch {eval $entrycmd} res] {set tag red}
         .t insert end $res\n $tag
         .t see end
         set entrycmd ""
     }
    bind .e <Up>   {history:move -1}
    bind .e <Down> {history:move 1}
    bind .e <Next> {history:move 99999}

     pack [text .t -height 5 -bg gray80] -fill x -side bottom
     .t tag configure red  -foreground red
     .t tag configure blue -foreground blue
     .t insert end "Welcome to Turtleshell!" red
     .t insert end " (Richard Suchenwirth 2000)
     All Tcl/Tk commands welcome, plus a few known from Logo:
     fd bk rt lt pu pd home setpc setbg...
     Enjoy!
     "
     frame .f
     foreach i {cs home demo} {
         button .f.$i -text $i -command $i -width 4 -pady 0
     }
     foreach i {red orange yellow green1 green3 blue purple black white} {
         button .f.$i -background $i -width 2 -pady 0 -command "setpc $i"
         bind   .f.$i <3> "setbg $i"
     }
     eval pack [winfo children .f] -side left
     pack .f -side bottom -pady 5 -fill x

     canvas .c -bg black -width 400 -height 300 \
             -scrollregion {-200 -150 200 150}
     pack .c -fill both -expand 1 -side top
     #-------------------------- Doodler
     bind .c <ButtonPress-1> {
         set X [%W canvasx %x]
         set Y [%W canvasy %y]
         set %W(line) [list %W coords [%W create line \
                 $X $Y $X $Y -fill $Turtle::data(fg)] $X $Y]
     }
     bind .c <B1-Motion> {
         eval [lappend %W(line) [%W canvasx %x] [%W canvasy %y]]}
     bind .c <ButtonRelease-1> {unset %W(line)}

     update
     Turtle::Init .c

     to square s {repeat 4 {fd $s rt 90}}
     to web s {repeat 36 {square $s rt 10}}
     ht setpc yellow web 30 web 50 web 80 st
     focus .e
 }
  proc demo {{var ::entrycmd}} {
     set it [random:select $::Turtle::demos]
     .t insert end "Now playing:\n$it\n"
     .t see end-2c
     cs; ht; setpc [random:select [colors]]
     eval $it; st
     upvar $var wait
     if {$wait==""} {after 3000 demo}
 }
 #----------------------------- history for entry widget
 set history {}; set nhistory 0
 proc history:add? {s} {
     if [string compare $s [lindex $::history end]] {
         lappend ::history $s
         set ::nhistory [llength $::history]
     }
 }
 proc history:move {where} {
     incr ::nhistory $where
     if {$::nhistory<0} {set ::nhistory 0}
     if {$::nhistory>=[llength $::history]+1} {
         set ::nhistory [llength $::history]
     }
     set ::entrycmd [lindex $::history $::nhistory]
 }

 turtleshell

  using the console show command (eTCL)
  Only change statement and additional code shown below.
   The help statements call and print on the console.

        namespace export -clear bk clean cs fd home ht lt pd pu rt \
                setbg seth setpc setpos setx sety st help to

     to help   {} {console show}

  foreach i {cs home demo exit help} {
         button .f.$i -text $i -command $i -width 4 -pady 0
     }
    puts "
 bk   - move back (n pixels)
 cs   - clear screen
 fd   - move forward (n pixels, drawing a line if pen is down)
 home - move turtle to (0,0)
 ht   - hide turtle (a triangular cursor indicating drawing direction)
 lt   - left turn (in degrees)
 pd   - pen down
 pu   - pen up
 rt   - right turn (in degrees)
 st   - show turtle
     "

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