Tk-powered Ruby turtle graphics
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Trtl - Simple Ruby Turtle Graphics

example session


gem install trtl


Trtl is a simple 'turtle' system inspired by Python's It provides simple turtle drawing capabilities in Ruby, even if you're just at an IRB prompt. It leans on Tk (which used to be in Ruby's standard library but is now an external gem).


If Trtl detects you're in an IRb or Pry session, it'll automatically make turtle methods available directly at the prompt. For example:

$ irb
> require 'trtl'
> forward 100
# At this point, a window appears with the turtle

If you wish to use Trtl from a regular Ruby script, you have a few options. You can create a Trtl instance and use it directly:

require 'trtl'
t =
10.times { t.left(24); t.forward(30); t.ensure_drawn }

You can use Trtl's run method to use it in a more interactive fashion: { 10.times { left(24); forward(30); ensure_drawn } }

Or you can include InteractiveTurtle and get a similar effect as if you were in IRb:

include InteractiveTurtle
10.times { left(24); forward(30) }

Note: Using InteractiveTurtle makes drawing slower as it ensures all graphics are drawn after every action (as necessary for IRb use).


Only a small number of commands are currently implemented, but they're enough for the major actions:

  • title(title_name)
  • forward(distance) - aliased as fd
  • back(distance) - aliased as bk and backward
  • left(angle) - aliased as lt
  • right(angle) - aliased as rt
  • pen_up - aliased as pu and up and penup
  • pen_down - aliased as pd and down and pendown
  • color(color_name) - aliased as pencolor
  • move(x, y) - aliased as goto
  • position - aliased as pos
  • circle(radius, extent = 360, steps = 360)
  • dot(size) - draws a dot, defaults to a sensible size but you can supply if you want
  • is_drawing?
  • width(width_in_pixels)


The examples in the examples folder should be reasonably illustrative. If you try any of them, try example4.rb - it renders an awesome looking tree.



Copyright and License

Copyright (c) 2012-2017 Peter Cooper (other than minor parts of some samples.)

MIT licensed. See