logo_turtle.red

turtle: #()

win: layout [ panel [ 
                tfield: base 500x500 white draw [] 
                origin tfield/offset tlayer: base 500x500 255.255.255.255 draw [] ]
              panel [
                text "History" return history: text-list 200x350 data [] return 
                panel [ button "Save" [save request-file history/data]
                        button "Load" [commands: load request-file foreach cmd commands [process-cmd cmd]] ]
                return status: text "" 200x25 ]
              return
              text "Command" cmdfield: field 300x25 [process-cmd cmdfield/text] 
              error: text 100x25 ]
              
home: func[] [
  turtle/position:  250x250
  turtle/color:     black
  turtle/direction: 0
  turtle/x: 255.0 turtle/y: 255.0
  turtle/pen-down:  true
  
]

reset: func[] [
  clear history/data
  clear tfield/draw
  turtle/visible: true
  turtle/procs: #()
  home
]

turn-by: func[degrees [integer!]] [
  turtle/direction: turtle/direction + degrees // 360
]

loc-pair: func[x y] [make pair! compose [(to integer! round x) (to integer! round y)]]

move-by: func[distance [integer!]] [
  delta: compose [x ((sine turtle/direction) * distance) y ((cosine turtle/direction) * distance)]
  if turtle/pen-down [ append/only tfield/draw
    compose [line (translate-loc loc-pair turtle/x turtle/y) (translate-loc loc-pair turtle/x + delta/x turtle/y + delta/y)]
  ]
  turtle/x: turtle/x + delta/x
  turtle/y: turtle/y + delta/y
  do-events/no-wait
  wait .1
]

translate-loc: func [loc [pair!]] [loc/y: 500 - loc/y loc]

set-color: func [color] [
  append/only tfield/draw compose [pen (color)]
]

redraw-turtle: func [] [
  clear tlayer/draw
  if turtle/visible [
    headpos: make pair! compose [(to integer! (sine turtle/direction) * 10) (to integer! (cosine turtle/direction) * 10)]
    append/only tlayer/draw compose [fill-pen green circle (translate-loc loc-pair turtle/x turtle/y) 10 
      circle (translate-loc (loc-pair turtle/x turtle/y) + headpos) 3 fill-pen off]
  ]
]

turtle-repeat: func [cnt rblk] [
  loop cnt [parse rblk parse-rules]
]

parse-rules: [
  some [
    ['fd | 'forward] set distance integer! (move-by distance) |
    ['bk | 'back] set distance integer! (move-by distance * -1) |
    ['rt | 'right] set degrees integer! (turn-by degrees) |
    ['lt | 'left] set degrees integer! (turn-by degrees * -1) |
    ['pu | 'penup] (turtle/pen-down: false) |
    ['pd | 'pendown] (turtle/pen-down: true) |    
    'color set value word! (set-color value) |
    'repeat set value integer! set blk block! (turtle-repeat value blk) |
    'to copy proc to 'end thru 'end (put turtle/procs proc/1 next proc) |
    'ht (turtle/visible: false) |
    'st (turtle/visible: true) |
    'reset (reset) |
    'clear (clear tfield/draw) |
    'home (home) |
    ['quit | 'q] (quit) |
    set word word! (either blk: select turtle/procs word [parse blk parse-rules] 
      [error/text: mold/only compose [Unknown Word (word)]]) break
  ]
]

process-cmd: func[cmd [string!]] [
  error/text: ""
  parse load/all cmd parse-rules
  if empty? error/text [append history/data cmd cmdfield/text: none ]
  redraw-turtle  
  status/text: mold/only compose [Position: (loc-pair turtle/x turtle/y) Direction: (turtle/direction) degrees]
]

process-cmd "reset"

view/no-wait win

Did some of my own tweaks to Logo_Turtle (not changed on github)
-Running on Win10

Line 10: increased status: text area from 200x25 to 200x100 (there wasn't enough room for text)
Line 13: increased error: text area from 100x25 to 300x25 (there wasn't enough room for text)
Line 97: Added the status of Pen Down (see below)
status/text: mold/only compose [Position: (loc-pair turtle/x turtle/y) Direction: (turtle/direction) degrees Pen Down: (turtle/pen-down)]

Bugs:
-Every second line does not draw (FD or BK at any angle)
-Does not appear to be due to toggling Pen Down. That is why I modified line 97.