Copyright (C) 2011 by David Scherer and Bruce Sherwood

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
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The above copyright notice and this permission notice shall be included in
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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.

Handling touch events is thanks to jQuery UI Touch Punch of David Furfero.
See http://touchpunch.furf.com.

(Implementation of spin/rotate/drag was independent of Touch Punch.)

Salvatore di Dio demonstrated in his RapydGlow experiment (http://salvatore.pythonanywhere.com/RapydGlow)
how he was able to use the RapydScript Python-to-JavaScript compiler with GlowScript graphics.
This inspired the implementation of the VPython (vpython.org) API at glowscript.org.
He provided the file papercomp.js for operator overloading, based on the work of
    Juerg Lehni (PaperScript: http://scratchdisk.com/posts/operator-overloading).
He also assembled support for operator overloading and the ability to write synchronous code
in the file transform-all.js, based on the work of
    Bruno Jouhier (Streamline: https://github.com/Sage/streamlinejs), and
    Marijn Haverbeke (Acorn.js: https://github.com/marijnh).
Supporting the VPython API in a browser is possible thanks to the work of
    Alexander Tsepkov (RapydScript: https://bitbucket.org/pyjeon/rapydscript) and
    Charles Law (browser-based RapydScript: http://pyjeon.pythonanywhere.com/static/rapydscript_online/index.html).

When the GlowScript project was launched in 2011 by David Scherer and Bruce Sherwood,
Scherer implemented operator overloading and synchronous code using libraries existing at that time.
In 2015 it became necessary to upgrade to newer libraries because compilation failed on some browsers.

Tessellation with multiple holes, JavaScript version: https://github.com/r3mi/poly2tri.js
For explanation of poly2tri, see http://sites-final.uclouvain.be/mema/Poly2Tri

Font manipulation: https://github.com/nodebox/opentype.js
Public-domain sans serif font Roboto-Medium.ttf from http://www.1001freefonts.com/roboto.font
Public-domain serif font NimbusRomNo9L-Med.otf from http://www.1001fonts.com/nimbus-roman-no9-l-font.html
