# Turtle graphics for the PicoCalc **URL:** \ **Category:** PicoCalc\ **Tags:** software\ **Created:** [July 11, 2026, 1:53am UTC](https://forum.clockworkpi.com/t/turtle-graphics-for-the-picocalc/22929 "2026-07-11T01:53:19Z")\ **Posts on this page:** 16\ **Page:** 1
**Author:** ![tabemann](https://avatars.discourse-cdn.com/v4/letter/t/df705f/32.png) [@tabemann](https://forum.clockworkpi.com/u/tabemann)\ **Post date:** [July 11, 2026, 1:53am UTC](https://forum.clockworkpi.com/t/turtle-graphics-for-the-picocalc/22929/1 "2026-07-11T01:53:19Z")
There appears to be two implementation of turtle graphics for the PicoCalc, Pico Logo by @BlairLeduc and my own `turtle` module under zeptoforth. For more information on Pico Logo, look at: > [@Pico Logo—A fun language for learning](https://forum.clockworkpi.com/t/pico-logo-a-fun-language-for-learning/20833): > > I am happy to announce the release of Pico Logo for the PicoCalc. Logo is a fun and easy way to program your PicoCalc! The project site includes a [full reference manual](https://github.com/BlairLeduc/pico-logo/blob/main/reference/Pico_Logo_Reference.md) to get you started with classic Logo fundamentals. In addition, the internet is full of resources to get started and then to advance to more complex solutions. Feature Highlights: 320×320 resolution turtle graphics with 256 colours (from a palette of 65K colours) Three simultaneous display modes: full screen text fo… Pico Logo, of course, is a full implementation of the Logo language, of which turtle graphics is sadly but the most well-known feature. (Logo is really a classic Lisp minus all the parens.) I personally remember Logo from when I was in elementary school, but they never taught us about its features beyond turtle graphics. (Even then, I knew it was a better language than BASIC, though.) The `turtle` module for zeptoforth, which can be seen at [`extra/rp_common/turtle_picocalc.fs`](https://github.com/tabemann/zeptoforth/blob/master/extra/rp_common/turtle_picocalc.fs), is another option. It is designed so its turtle graphics API is mostly compatible with that of Thurtle, a WAForth-based turtle graphics system that runs in the browser, and it has full access to the zeptoforth environment. I am surprised that no one here has come out with a turtle graphics system for MMBasic, as that would be something that seems like it would be natural to implement. Is this perhaps due to the limitations of libraries under MMBasic, or is there not enough room to implement turtle graphics as part of MMBasic itself (cf. the thread here about MMBasic being ‘done’)? Some key differences between the two is that Pico Logo, at least on the RP2350, uses floating-point, whereas the `turtle` module for zeptoforth’s API uses integers and it uses S31.32 fixed-point math internally. Other differences include that Pico Logo uses palette color with 256 colors selected from 65536 colors, whereas the `turtle` module for zeptoforth internally uses RGB332 color even though colors are selected as components of 0 to 255. I am surprised more people have not tried out Pico Logo, especially since Logo is actually an all-around very nice language. You guys should try it out! As for zeptoforth, it is not nearly as forgiving as Logo, e.g. if you recurse too deep you can cause undefined behavior or simply crash, requiring a reboot. Yet at the same time, if you want to use zeptoforth the `turtle` module provides easy means to draw graphics, and in most cases you can avoid writing code that uses words such as `@` or `!` which directly peek or poke memory. Of course, I cannot help but give out some info on turtle graphics under zeptoforth, so here goes… The API of the `turtle` module for zeptoforth consists of the following words: `setpencolor` ( r g b -- ) `setturtlecolor` ( r g b -- ) `forward` ( pixels -- ) `backward` ( pixels -- ) `left` ( degrees -- ) `right` ( degrees -- ) `penup` ( -- ) `pendown` ( -- ) `getpendown` ( -- pendown? ) `setxy` ( x y -- ) `getxy` ( -- x y ) `setheading` ( degrees -- ) `getheading` ( -- degrees ) `hideturtle` ( -- ) `showturtle` ( -- ) `getshowturtle` ( -- showturtle? ) `updateoff` ( -- ) `updateon` ( -- ) `getupdateon` ( -- updateon? ) `setpensize` ( pixels -- ) `getpensize` ( -- pixels ) `clear` ( -- ) `home` ( -- ) These should be self-explanatory, especially if you have dealt with turtle graphics elsewhere. Of course, this thread would not be complete without some screenshots, so here is one: ![SPINSQR](https://canada1.discourse-cdn.com/flex029/uploads/clockworkpi/original/3X/9/1/913ce7923f2a0a4b6c0985a85380b8d538328d8c.png) The code for this: ```plaintext begin-module spin-square turtle import : draw-spin-square ( -- ) page home clear penup 1 forward 90 right 1 forward 90 right pendown 200 2 ?do i forward 89 right loop ; end-module ``` ---
**Author:** ![Drogon](https://yyz1.discourse-cdn.com/flex029/user_avatar/forum.clockworkpi.com/drogon/32/16529_2.png) [@Drogon](https://forum.clockworkpi.com/u/Drogon)\ **Post date:** [July 11, 2026, 10:43am UTC](https://forum.clockworkpi.com/t/turtle-graphics-for-the-picocalc/22929/2 "2026-07-11T10:43:24Z")
> [@tabemann](#): > > There appears to be two implementation of turtle graphics for the PicoCalc, Pico Logo by @BlairLeduc and my own `turtle` module under zeptoforth. My BCPL OS fully supports Turtle graphics too. Here is your spinny square: ![spin](https://canada1.discourse-cdn.com/flex029/uploads/clockworkpi/original/3X/1/7/175371e3190b98cb3b6252c23fb7d947f483c697.png) Code: ```plaintext GET "libhdr" GET "math" GET "vdu" LET d2r (d) = d #* M_DEG2R AND spin () BE { vduCls () turtlePen (0) turtleMoveTo (160, 160) turtlePen (1) FOR i = 2 TO 200 DO { turtleMove (i) turtleTurn (d2r (89.0)) } } AND start () = VALOF { turtleInit () turtleColour (colMustard) spin () RESULTIS 0 } ``` -Gordon ---
**Author:** ![BlairLeduc](https://yyz1.discourse-cdn.com/flex029/user_avatar/forum.clockworkpi.com/blairleduc/32/11808_2.png) [@BlairLeduc](https://forum.clockworkpi.com/u/BlairLeduc)\ **Post date:** [July 11, 2026, 12:26pm UTC](https://forum.clockworkpi.com/t/turtle-graphics-for-the-picocalc/22929/3 "2026-07-11T12:26:30Z")
Thank you, @tabemann! That is a great comparison. Logo needs a strong recursion capability since recursion as it is a well used technique in algorithms in the language. TCO (Tail-Call Optimization) allows for infinite recursion if your Logo procedure is implemented to harness it. The examples above in Forth and BCPL can be writing in Logo as: ```logo cs repeat 200 [fd repcount rt 89] ``` ---
**Author:** ![Toml\_12953](https://yyz1.discourse-cdn.com/flex029/user_avatar/forum.clockworkpi.com/toml_12953/32/11925_2.png) [@Toml\_12953](https://forum.clockworkpi.com/u/Toml_12953)\ **Post date:** [July 11, 2026, 1:56pm UTC](https://forum.clockworkpi.com/t/turtle-graphics-for-the-picocalc/22929/4 "2026-07-11T13:56:44Z")
Are you not aware of the built-in turtle graphics in MMBasic? Here’s a summary of commands: ```auto Appendix H – Turtle Graphics Turtle Graphics This release contains a very comprehensive turtle graphics implementation for all versions except the WebMite RP2040 and WebMite RP2350. The supported commands with “TURTLE “ prepended are: Movement Commands FORWARD distance (FD) - Move forward by distance pixels BACK distance (BK) - Move backward by distance pixels [TURN] LEFT [angle] (LT) - Turn left by angle degrees, 90 degrees if not specified [TURN] RIGHT [angle] (RT) - Turn right by angle degrees, 90 degrees if not Position Commands SET XY x, y - Move to absolute position (x,y) SET X x - Set X coordinate, keep Y SET Y y - Set Y coordinate, keep X SET HEADING angle (SETH) - Set absolute heading (0=up, 90=right) HOME - Return to center (MM.HRES\2,MM.VRES\2) heading 0 Pen Control Commands PEN UP (PU) - Lift pen (stop drawing) PEN DOWN (PD) - Lower pen (start drawing) PEN COLOUR color (PC) - Set pen color PEN WIDTH width (PW) - Set pen line width Arc and Curve Commands ARC radius angle - Draw arc with given radius and angle ARCLEFT radius,angle (ARCL) - Draw arc turning left ARCRIGHT radius,angle (ARCR) - Draw arc turning right BEZIER cp1 , cp1angle, cp2, cp2angle, end, endangle - Draw Bezier curve with control points Basic Shape Commands CIRCLE radius - Draw circle at current position DOT size - Draw filled dot (default size=5) FCIRCLE radius - Draw filled circle FRECTANGLE width,height (FRECT) - Draw filled rectangle WEDGE radius start end - Draw filled wedge/pie slice Fill Commands FILL COLOUR color (FC) - Set fill color and enable filling FILL PATTERN pattern (FP) - Set fill pattern (0-31) NO FILL - Disable filling FILL - Flood fill at current position BEGIN FILL (BF) - Start recording polygon for fill END FILL (EF) - End recording and fill polygon Cursor Commands SHOW TURTLE (ST) - Show turtle cursor HIDE TURTLE (HT) - Hide turtle cursor CURSOR SIZE size (CS) - Set cursor size CURSOR COLOUR color CC) - Set cursor color STAMP - Draw a turtle at the current x,y position State Management Commands RESET [show] - clear screen and reset everything, show the turtle if show = 1 PUSH - Save current position and heading to stack POP - Restore position and heading from stack ``` ---
**Author:** ![tabemann](https://avatars.discourse-cdn.com/v4/letter/t/df705f/32.png) [@tabemann](https://forum.clockworkpi.com/u/tabemann)\ **Post date:** [July 11, 2026, 4:20pm UTC](https://forum.clockworkpi.com/t/turtle-graphics-for-the-picocalc/22929/5 "2026-07-11T16:20:29Z")
Sorry for forgetting about your turtle graphics implementation ─ and yes, now that I think of it, I _have_ seen you post demos of it in action! ---
**Author:** ![tabemann](https://avatars.discourse-cdn.com/v4/letter/t/df705f/32.png) [@tabemann](https://forum.clockworkpi.com/u/tabemann)\ **Post date:** [July 11, 2026, 4:22pm UTC](https://forum.clockworkpi.com/t/turtle-graphics-for-the-picocalc/22929/6 "2026-07-11T16:22:00Z")
Thanks for posting this! I must just never have noticed since while there have been _many_ graphical demos for MMBasic posted here, I hadn’t recalled seeing any that actually used turtle graphics. ---
**Author:** ![Drogon](https://yyz1.discourse-cdn.com/flex029/user_avatar/forum.clockworkpi.com/drogon/32/16529_2.png) [@Drogon](https://forum.clockworkpi.com/u/Drogon)\ **Post date:** [July 11, 2026, 5:09pm UTC](https://forum.clockworkpi.com/t/turtle-graphics-for-the-picocalc/22929/7 "2026-07-11T17:09:24Z")
So here is a Turtle challenge 😉 A few years back, Randall Munroe of XKCD fame, posted a lovely piece of art with an obvious nod to Bob Ross > **[xkcd: Instructions](https://xkcd.com/2601/)** the original was in Logo, but the challenge here is to re-do it in language of your choice (Probably rules out Blair 😉 I did it back then in my own RTB Basic dialect and used some automation which I wrote in Basic to do the conversion. [![](https://img.youtube.com/vi/3W554EUs2To/maxresdefault.jpg "XKCD 2601 in RTB BASIC") ](https://www.youtube.com/watch?v=3W554EUs2To) Enjoy 🙂 -Gordon ---
**Author:** ![tabemann](https://avatars.discourse-cdn.com/v4/letter/t/df705f/32.png) [@tabemann](https://forum.clockworkpi.com/u/tabemann)\ **Post date:** [July 11, 2026, 5:20pm UTC](https://forum.clockworkpi.com/t/turtle-graphics-for-the-picocalc/22929/8 "2026-07-11T17:20:33Z")
I would implement that, but I’d first want an actual code listing in text of the Logo code being read off. Apparently the audio for that xkcd is more than 8 _hours_ long, and I am not going to sit through it, nor does [explainxkcd](https://www.explainxkcd.com/wiki/index.php/2601:_Instructions) seem to provide a direct code listing that I could work off of. ---
**Author:** ![picouser](https://avatars.discourse-cdn.com/v4/letter/p/e495f1/32.png) [@picouser](https://forum.clockworkpi.com/u/picouser)\ **Post date:** [July 11, 2026, 6:05pm UTC](https://forum.clockworkpi.com/t/turtle-graphics-for-the-picocalc/22929/9 "2026-07-11T18:05:29Z")
here is a very simple MMBasic example of turtle graphics ’ Hilbert Curve for 320x240 displays ’ Based on original by “Sasquatch” Dim cmap(15)=(RGB(black),RGB(blue),RGB(myrtle),RGB(cobalt),RGB(midgreen),RGB(cerulean),RGB(green),RGB(cyan),RGB(red),RGB(magenta),RGB(rust),RGB(fuchsia),RGB(brown),RGB(lilac),RGB(yellow),RGB(white)) Dim k$ C = 1 '-------------------------- ’ Pattern 1 '-------------------------- Turtle RESET Text 0,0,“Hilbert Curve (1 of 2)”,“”,2 Text 2,16,“Press Q to Quit, any other key for next”," ",1 Turtle PEN UP Turtle MOVE 10,210 Turtle PEN DOWN HILBERT(5,90,6) Text 0,0,“Hilbert Curve (1 of 2)”,“”,2 Text 2,16,“Press Q to Quit, any other key for next”," ",1 If k$=“” Then k$=we.wait\_for\_key$() If we.is\_quit\_key%(k$) Then End k$=“” we.clear\_keyboard\_buffer() '-------------------------- ’ Pattern 2 '-------------------------- Turtle RESET Text 0,0,“Hilbert Curve (2 of 2)”,“”,2 Text 2,16,“Press Q to Quit”,“”,1 Turtle PEN UP Turtle MOVE 90,220 Turtle PEN DOWN HILBERT(6,90,2) If Not we.is\_quit\_key%(k$) Then we.wait\_for\_quit() End Sub HILBERT(Level,Angle,Length) If k$=“” Then k$=Inkey$ If k$\<\>“” Then Exit Sub If Level=0 Then Exit Sub C=C+0.1 Turtle PEN COLOUR cMap(C Mod 14 +1) TurnTurtle(Angle) HILBERT(Level-1,-Angle,Length) Turtle FORWARD Length TurnTurtle(-Angle) HILBERT(Level-1,Angle,Length) Turtle FORWARD Length HILBERT(Level-1,Angle,Length) TurnTurtle(-Angle) Turtle FORWARD Length HILBERT(Level-1,-Angle,Length) TurnTurtle(Angle) End Sub Sub TurnTurtle(Angle) If Angle\>0 Then Turtle TURN RIGHT Angle ElseIf Angle\<0 Then Turtle TURN LEFT Abs(Angle) EndIf End Sub Sub we.clear\_keyboard\_buffer() Do While Inkey$\<\>“” Loop End Sub Function we.is\_quit\_pressed%() If Not we.quit% Then we.quit%=we.is\_quit\_key%(Inkey$) EndIf we.is\_quit\_pressed%=we.quit% End Function Function we.is\_quit\_key%(k$) we.is\_quit\_key%=UCASE$(k$)=“Q” End Function Function we.wait\_for\_key$() Local k$ Do While k$=“” k$=Inkey$ Pause 100 Loop If we.is\_quit\_key%(k$) Then we.quit%=1 we.wait\_for\_key$=k$ End Function Sub we.wait\_for\_quit() Local k$ Do While Not we.quit% k$=we.wait\_for\_key$() Loop End Sub ---
**Author:** ![tabemann](https://avatars.discourse-cdn.com/v4/letter/t/df705f/32.png) [@tabemann](https://forum.clockworkpi.com/u/tabemann)\ **Post date:** [July 11, 2026, 8:22pm UTC](https://forum.clockworkpi.com/t/turtle-graphics-for-the-picocalc/22929/10 "2026-07-11T20:22:01Z")
I ported your Hilbert curve implementation to zeptoforth at [`test/rp_common/picocalc_turtle_hilbert.fs`](https://github.com/tabemann/zeptoforth/blob/master/test/rp_common/picocalc_turtle_hilbert.fs). Here is a screenshot: ![HILBERT2](https://canada1.discourse-cdn.com/flex029/uploads/clockworkpi/original/3X/6/3/63df90e4c169966cb7814d14b6bb4f0e9accdaec.png) And here is the source code: ```plaintext \ Copyright (c) 2026 Travis Bemann \ \ Permission is hereby granted, free of charge, to any person obtaining a copy \ of this software and associated documentation files (the "Software"), to deal \ in the Software without restriction, including without limitation the rights \ to use, copy, modify, merge, publish, distribute, sublicense, and/or sell \ copies of the Software, and to permit persons to whom the Software is \ furnished to do so, subject to the following conditions: \ \ The above copyright notice and this permission notice shall be included in \ all copies or substantial portions of the Software. \ \ THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR \ IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, \ FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE \ AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER \ LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, \ OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE \ SOFTWARE. begin-module hilbert turtle import create colors 0 c, 0 c, 0 c, 0 c, 0 c, 255 c, 0 c, 64 c, 0 c, 0 c, 64 c, 255 c, 0 c, 128 c, 0 c, 0 c, 128 c, 255 c, 0 c, 255 c, 0 c, 0 c, 255 c, 255 c, 255 c, 0 c, 0 c, 255 c, 0 c, 255 c, 255 c, 64 c, 0 c, 255 c, 64 c, 255 c, 255 c, 128 c, 0 c, 255 c, 128 c, 255 c, 255 c, 255 c, 0 c, 255 c, 255 c, 255 c, cell align, 1,0 2value color : set-color { index -- } index 3 * to index colors index + c@ colors index 1+ + c@ colors index 2 + + c@ setpencolor ; defer hilbert-unit :noname { level angle length -- } key? if exit then level 0= if exit then 0,1 color d+ to color color 14,0 fmod 1,0 d+ round-zero set-color angle right level 1- angle negate length hilbert-unit length forward angle left level 1- angle length hilbert-unit length forward level 1- angle length hilbert-unit angle left length forward level 1- angle negate length hilbert-unit angle right ; is hilbert-unit : setup-turtle ( x y -- ) page home clear penup setxy pendown ; : drop-keys ( -- ) begin key? while key drop repeat ; : draw-hilbert1 ( -- ) -150 -50 setup-turtle 5 90 6 hilbert-unit drop-keys ; : draw-hilbert2 ( -- ) -70 -60 setup-turtle 6 90 2 hilbert-unit drop-keys ; end-module ``` ---
**Author:** ![Toml\_12953](https://yyz1.discourse-cdn.com/flex029/user_avatar/forum.clockworkpi.com/toml_12953/32/11925_2.png) [@Toml\_12953](https://forum.clockworkpi.com/u/Toml_12953)\ **Post date:** [July 12, 2026, 3:06am UTC](https://forum.clockworkpi.com/t/turtle-graphics-for-the-picocalc/22929/11 "2026-07-12T03:06:21Z")
Here’s the program in MMBasic: ```auto TURTLE reset TURTLE pen colour RGB(YELLOW) TURTLE set xy 160, 160 FOR i = 2 TO 200 TURTLE forward i TURTLE turn right 89 NEXT i ``` ---
**Author:** ![tabemann](https://avatars.discourse-cdn.com/v4/letter/t/df705f/32.png) [@tabemann](https://forum.clockworkpi.com/u/tabemann)\ **Post date:** [July 12, 2026, 3:49am UTC](https://forum.clockworkpi.com/t/turtle-graphics-for-the-picocalc/22929/12 "2026-07-12T03:49:31Z")
Here is a more elaborate space-filling curve than the Hilbert curve implemented with turtle graphics as an Lindenmayer system, specifically the Gosper curve. The source code is at [`test/rp_common/picocalc_turtle_gosper.fs`](https://github.com/tabemann/zeptoforth/blob/master/test/rp_common/picocalc_turtle_gosper.fs). Here is a screenshot: ![GOSPER](https://canada1.discourse-cdn.com/flex029/uploads/clockworkpi/original/3X/3/c/3c32680c1d576dca8d45d9116a280d4dd0535aa3.png) And here is the source code: ```plaintext \ Copyright (c) 2026 Travis Bemann \ \ Permission is hereby granted, free of charge, to any person obtaining a copy \ of this software and associated documentation files (the "Software"), to deal \ in the Software without restriction, including without limitation the rights \ to use, copy, modify, merge, publish, distribute, sublicense, and/or sell \ copies of the Software, and to permit persons to whom the Software is \ furnished to do so, subject to the following conditions: \ \ The above copyright notice and this permission notice shall be included in \ all copies or substantial portions of the Software. \ \ THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR \ IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, \ FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE \ AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER \ LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, \ OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE \ SOFTWARE. begin-module gosper turtle import : rgb { D: r D: g D: b -- r g b } r 255,0 f* round-zero g 255,0 f* round-zero b 255,0 f* round-zero ; : convert-color { D: f -- r g b } f 6,0 f* to f f 1,0 d< if 1,0 f 0,0 rgb exit then f 2,0 d< if 2,0 f d- 1,0 0,0 rgb exit then f 3,0 d< if 0,0 1,0 f 2,0 d- rgb exit then f 4,0 d< if 0,0 4,0 f d- 1,0 rgb exit then f 5,0 d< if f 4,0 d- 0,0 1,0 rgb exit then 1,0 0,0 6,0 f d- rgb ; 0,1 16,0 f/ 2constant color-incr defer gosper-unit-a defer gosper-unit-b :noname ( level length D: color -- D: color' ) 2swap { level length } key? if exit then level 0> if -1 +to level level length 2swap gosper-unit-a 60 right level length 2swap gosper-unit-b 120 right level length 2swap gosper-unit-b 60 left level length 2swap gosper-unit-a 120 left level length 2swap gosper-unit-a level length 2swap gosper-unit-a 60 left level length 2swap gosper-unit-b 60 right else 2dup convert-color setpencolor color-incr d+ 1,0 fmod length forward then ; is gosper-unit-a :noname ( level length D: color -- D: color' ) 2swap { level length } key? if exit then level 0> if -1 +to level 60 left level length 2swap gosper-unit-a 60 right level length 2swap gosper-unit-b level length 2swap gosper-unit-b 120 right level length 2swap gosper-unit-b 60 right level length 2swap gosper-unit-a 120 left level length 2swap gosper-unit-a 60 left level length 2swap gosper-unit-b else 2dup convert-color setpencolor color-incr d+ 1,0 fmod length forward then ; is gosper-unit-b : drop-keys ( -- ) begin key? while key drop repeat ; : draw-gosper ( -- ) page home -64 32 setxy clear hideturtle 4 3 0,0 gosper-unit-a 2drop showturtle drop-keys ; end-module ``` ---
**Author:** ![tabemann](https://avatars.discourse-cdn.com/v4/letter/t/df705f/32.png) [@tabemann](https://forum.clockworkpi.com/u/tabemann)\ **Post date:** [July 13, 2026, 2:45am UTC](https://forum.clockworkpi.com/t/turtle-graphics-for-the-picocalc/22929/13 "2026-07-13T02:45:12Z")
I know someone has done this before in the graphical demos thread, but as long as we’re doing Lindenmayer systems with turtle graphics I figured I’d do a colored Lévy C curve. My source code is at [`test/rp_common/picocalc_turtle_levyc.fs`](https://github.com/tabemann/zeptoforth/blob/master/test/rp_common/picocalc_turtle_levyc.fs). Here is a screenshot: ![LEVYC](https://canada1.discourse-cdn.com/flex029/uploads/clockworkpi/original/3X/5/4/54aa21cb207ec58b9f6556b7d0ca36573d80e997.png) And here is a source code listing: ```plaintext \ Copyright (c) 2026 Travis Bemann \ \ Permission is hereby granted, free of charge, to any person obtaining a copy \ of this software and associated documentation files (the "Software"), to deal \ in the Software without restriction, including without limitation the rights \ to use, copy, modify, merge, publish, distribute, sublicense, and/or sell \ copies of the Software, and to permit persons to whom the Software is \ furnished to do so, subject to the following conditions: \ \ The above copyright notice and this permission notice shall be included in \ all copies or substantial portions of the Software. \ \ THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR \ IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, \ FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE \ AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER \ LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, \ OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE \ SOFTWARE. begin-module levyc turtle import : rgb { D: r D: g D: b -- r g b } r 255,0 f* round-zero g 255,0 f* round-zero b 255,0 f* round-zero ; : convert-color { D: f -- r g b } f 6,0 f* to f f 1,0 d< if 1,0 f 0,0 rgb exit then f 2,0 d< if 2,0 f d- 1,0 0,0 rgb exit then f 3,0 d< if 0,0 1,0 f 2,0 d- rgb exit then f 4,0 d< if 0,0 4,0 f d- 1,0 rgb exit then f 5,0 d< if f 4,0 d- 0,0 1,0 rgb exit then 1,0 0,0 6,0 f d- rgb ; 0,1 16,0 f/ 2constant color-incr 0 value length 0,0 2value color defer levyc-unit :noname { level -- } key? if exit then level 0> if -1 +to level 45 right level levyc-unit 90 left level levyc-unit 45 right else color convert-color setpencolor color color-incr d+ 1,0 fmod to color length forward then ; is levyc-unit : drop-keys ( -- ) begin key? while key drop repeat ; : draw-levyc ( -- ) page home 0 -60 setxy clear hideturtle 2 to length 0,0 to color 12 levyc-unit showturtle drop-keys ; end-module ``` ---
**Author:** ![tabemann](https://avatars.discourse-cdn.com/v4/letter/t/df705f/32.png) [@tabemann](https://forum.clockworkpi.com/u/tabemann)\ **Post date:** [July 15, 2026, 1:47am UTC](https://forum.clockworkpi.com/t/turtle-graphics-for-the-picocalc/22929/14 "2026-07-15T01:47:54Z")
I created another demo of a multicolored plant using turtle graphics under zeptoforth. It needs the latest version of [`extra/rp_common/turtle_picocalc.fs`](https://github.com/tabemann/zeptoforth/blob/master/extra/rp_common/turtle_picocalc.fs) because it uses the new words `turtle::fgetxy` and `turtle::fsetxy` to _exactly_ get and set the turtle position. One could consider it to be cheating because it saves and then later directly sets the turtle position and heading, mind you. You can get the source code from [`test/rp_common/picocalc_turtle_plant.fs`](https://github.com/tabemann/zeptoforth/blob/master/test/rp_common/picocalc_turtle_plant.fs). Here is a screenshot: ![PLANT](https://canada1.discourse-cdn.com/flex029/uploads/clockworkpi/original/3X/f/9/f91084116d7494e5568a1a01b606d243babffba6.png) And here is a listing of the source code: ```plaintext \ Copyright (c) 2026 Travis Bemann \ \ Permission is hereby granted, free of charge, to any person obtaining a copy \ of this software and associated documentation files (the "Software"), to deal \ in the Software without restriction, including without limitation the rights \ to use, copy, modify, merge, publish, distribute, sublicense, and/or sell \ copies of the Software, and to permit persons to whom the Software is \ furnished to do so, subject to the following conditions: \ \ The above copyright notice and this permission notice shall be included in \ all copies or substantial portions of the Software. \ \ THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR \ IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, \ FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE \ AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER \ LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, \ OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE \ SOFTWARE. begin-module plant turtle import : rgb { D: r D: g D: b -- r g b } r 255,0 f* round-zero g 255,0 f* round-zero b 255,0 f* round-zero ; : convert-color { D: f -- r g b } f 6,0 f* to f f 1,0 d< if 1,0 f 0,0 rgb exit then f 2,0 d< if 2,0 f d- 1,0 0,0 rgb exit then f 3,0 d< if 0,0 1,0 f 2,0 d- rgb exit then f 4,0 d< if 0,0 4,0 f d- 1,0 rgb exit then f 5,0 d< if f 4,0 d- 0,0 1,0 rgb exit then 1,0 0,0 6,0 f d- rgb ; 0,1 16,0 f/ 2constant color-incr 0 value length 0,0 2value color begin-structure frame-size 2field: frame-x 2field: frame-y field: frame-heading end-structure : push ( -- ) here { frame } frame-size allot fgetxy frame frame-y 2! frame frame-x 2! getheading frame frame-heading ! ; : pop ( -- ) penup here frame-size - { frame } frame frame-x 2@ frame frame-y 2@ fsetxy frame frame-heading @ setheading [frame-size negate] literal allot pendown ; defer plant-x-unit defer plant-f-unit :noname { level -- } key? if exit then level 0> if -1 +to level level plant-f-unit 25 left push push level plant-x-unit pop 25 right level plant-x-unit pop 25 right level plant-f-unit push 25 right level plant-f-unit level plant-x-unit pop 25 left level plant-x-unit then ; is plant-x-unit :noname { level -- } key? if exit then level 0> if -1 +to level level plant-f-unit level plant-f-unit else color convert-color setpencolor color color-incr d+ 1,0 fmod to color length forward then ; is plant-f-unit : drop-keys ( -- ) begin key? while key drop repeat ; : draw-plant ( -- ) page home -130 -160 setxy 25 right clear hideturtle 2 to length 0,0 to color 6 plant-x-unit showturtle drop-keys ; end-module ``` ---
**Author:** ![maple](https://yyz1.discourse-cdn.com/flex029/user_avatar/forum.clockworkpi.com/maple/32/12677_2.png) [@maple](https://forum.clockworkpi.com/u/maple)\ **Post date:** [July 15, 2026, 4:07pm UTC](https://forum.clockworkpi.com/t/turtle-graphics-for-the-picocalc/22929/15 "2026-07-15T16:07:37Z")
are these not that? [2601: Instructions/Audio Transcript - explain xkcd](https://www.explainxkcd.com/wiki/index.php/2601:_Instructions/Audio_Transcript) ---
**Author:** ![tabemann](https://avatars.discourse-cdn.com/v4/letter/t/df705f/32.png) [@tabemann](https://forum.clockworkpi.com/u/tabemann)\ **Post date:** [July 15, 2026, 7:21pm UTC](https://forum.clockworkpi.com/t/turtle-graphics-for-the-picocalc/22929/16 "2026-07-15T19:21:59Z")
I should have looked closer – when I saw ‘transcript’ I assumed it was just a raw transcript of what was being said, rather than actual code.