31:T523,md`[CindyJS](https://cindyjs.org) ([GitHub](https://github.com/CindyJS/CindyJS)) is a mathematically-oriented JavaScript framework for **interactive** 2D and 3D geometry, developed by geometers at TU Munich and University of Potsdam. It provides an interpreter for the scripting language CindyScript, originally developed for the [Cinderella project (in Java)](https://cinderella.de) by [Jürgen Richter-Gebert](https://www-m10.ma.tum.de/bin/view/Lehrstuhl/RichterGebert) and [Ulrich Kortenkamp](https://kortenkamps.net/). The interactive (!) presentations on [this page](https://cindyjs.org/pub/2016-icms/) by the CindyJS team are a great intro to the project. More examples of CindyJS in action can be seen in [the gallery of the project site](https://cindyjs.org/gallery/) or the [Math to Touch](https://imaginary.github.io/applauncher2/) page. [I take zero credit for the beautiful examples in this notebook: the hard parts were copy-pasted from the CindyJS website / repository! Also note that I'm not affiliated with the CindyJS project, and I have barely any experience with CindyScript -- feel free to DM me for help ([@blockspins](https://twitter.com/blockspins)), but deep questions are probably better asked at GitHub or [the Cinderella forums](https://cinderella.de/tiki-view_forum.php?forumId=1).] `32:T486,md`The original source for the example shown above is [here](https://github.com/CindyJS/website/blob/master/src/gallery/main/JuliaConjugated/JuliaConjugated.html). To understand how CindyJS works (and how I got this running in Observable), let's have a look at the source for the cell [\`juliaCanvas\`](#juliaCanvas) at the top of this notebook: \`\`\`html html\`

\` \`\`\` CindyJS creates a child HTML canvas element inside the \`div\`, which it finds by its \`id\`. Remember to specify the height and width of the \`div\` up front as otherwise Observable may fail to detect its size change and [cells might end up overlapping](https://talk.observablehq.com/t/overlap-of-cells-with-output/246). The next cell contains the invocation of \`CindyJS\`. See the API reference [here](https://github.com/CindyJS/CindyJS/blob/master/ref/createCindy.md). Note that we call the \`startup()\` method explicitly in Observable; this may not be necessary in CindyJS embedded on an ordinary webpage. Similarly, we make sure that the \`shutdown()\` method runs if the cell becomes invalidated.`33:T774,bouncerCindy = { bounceCanvas; cdyBounceInit; cdyBounceMove; const bouncer = CindyJS.newInstance({ defaultAppearance: { dimDependent: 0.7 }, movescript: "bouncemove", initscript: "bounceinit", geometry: [ { name: "A", type: "Free", pos: [-5, 5], color: [1, .5, .5] }, { name: "B", type: "Free", pos: [-9, 7], color: [0, 0, 0], size: 3 }, { name: "C", type: "Free", pos: [-7, -8], color: [0, 0, 0], size: 3 }, { name: "D", type: "Free", pos: [7, -8], color: [0, 0, 0], size: 3 }, { name: "E", type: "Free", pos: [9, 7], color: [0, 0, 0], size: 3 }, { name: "F", type: "Free", pos: [-3, -4], color: [0, 0, 0], size: 3 }, { name: "G", type: "Free", pos: [1, -2], color: [0, 0, 0], size: 3 }, { name: "a", type: "Segment", args: ["B", "C"], color: [0, 0, 0], size: 1 }, { name: "b", type: "Segment", args: ["C", "D"], color: [0, 0, 0], size: 1 }, { name: "c", type: "Segment", args: ["D", "E"], color: [0, 0, 0], size: 1 }, { name: "d", type: "Segment", args: ["F", "G"], color: [0, 0, 0], size: 1 } ], behavior: [ { behavior: { type: "Environment", gravity: -.2 } }, { name: "A", behavior: { type: "Mass", friction: 0.0, vx: 0.3 } }, { name: "a", behavior: { type: "Bouncer" } }, { name: "b", behavior: { type: "Bouncer" } }, { name: "c", behavior: { type: "Bouncer" } }, { name: "d", behavior: { type: "Bouncer" } } ], autoplay: true, ports: [ { id: "Bouncer", width: 300, height: 300, transform: [{ visibleRect: [-10, -10, 10, 10] }] } ] }); bouncer.startup(); invalidation.then(() => bouncer.shutdown()); return bouncer; }34:T515,fernCindy = { fernCanvas; cdyFernInit; cdyFernKeydown; cdyFernMove; const gslp = [ { name: "A", type: "Free", pos: [-2.064, 4.404] }, { name: "A1", type: "Free", pos: [-0.0206, 0.7046] }, { name: "A2", type: "Free", pos: [-1.5782, 5.426] }, { name: "A3", type: "Free", pos: [-1.5578, 2.0942] }, { name: "A4", type: "Free", pos: [1.5427, 0.9603] }, { name: "B", type: "Free", pos: [2.378, 3.528] }, { name: "B1", type: "Free", pos: [0.0238, 0.5645] }, { name: "B2", type: "Free", pos: [2.1624, 4.5037] }, { name: "B3", type: "Free", pos: [-0.4417, 2.9231] }, { name: "B4", type: "Free", pos: [0.6311, 1.905] }, { name: "C", type: "Free", pos: [2.636, 9.974], alpha: 0 }, { name: "C1", type: "Free", pos: [0.0264, 1.5958] } //{ name: "C2", type: "Free", pos: [2.6396, 9.9725]}, //{ name: "C3", type: "Free", pos: [-2.066, 4.4006]}, //{ name: "C4", type: "Free", pos: [2.3973, 3.5191]}, ]; const fern = CindyJS({ scripts: "fern*", geometry: gslp, animation: { autoplay: true }, ports: [ { id: "FernCanvas", width: 400, height: 800, transform: [{ visibleRect: [-3, -1, 4, 13] }] } ] }); fern.startup(); invalidation.then(() => fern.shutdown()); return fern; }35:T2a7b,LICENSE = "Apache v2"/* Apache License Version 2.0, January 2004 http://www.apache.org/licenses/ TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION 1. 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`","pinned":false,"hidden":false,"mode":"ojs"},{"id":306,"value":"$31","pinned":false,"hidden":false,"mode":"ojs"},{"id":297,"value":"md`## Importing CindyJS / CindyGL / CindyJS.css`","pinned":false,"hidden":false,"mode":"ojs"},{"id":349,"value":"md`We can import CindyJS and its plugin CindyGL using this technique from [@tcmw](https://beta.observablehq.com/@tmcw)'s notebook \"[🤔 How to: require stubborn modules](https://beta.observablehq.com/@tmcw/requiring-modules-troubleshooting#THREE)\".`","pinned":false,"hidden":false,"mode":"ojs"},{"id":4,"value":"CindyJS = {\n const CindyJS = window.CindyJS = await require('https://cindyjs.org/dist/latest/Cindy.js').catch(() => window.CindyJS);\n await require('https://cindyjs.org/dist/latest/CindyGL.js').catch(() => {});\n return CindyJS;\n}","pinned":true,"hidden":false,"mode":"ojs"},{"id":358,"value":"md`If CindyGL is not needed, the following one-liner works:\n\n\\`\\`\\`js\nCindyJS = await require('https://cindyjs.org/dist/latest/Cindy.js').catch(() => window.CindyJS)\n\\`\\`\\`\n\nCindyJS.css is required for buttons constructed in CindyScript to work, according to [this GitHub issue](https://github.com/CindyJS/CindyJS/issues/683#issuecomment-404515607) [none are used in this notebook yet though]:`","pinned":false,"hidden":false,"mode":"ojs"},{"id":291,"value":"CindyJScss = html``","pinned":true,"hidden":false,"mode":"ojs"},{"id":571,"value":"md`Here's a little helper function for including CindyScript in Observable notebooks. Use \\`cdy(myid)\\` as a template literal tag ahead of \\`\\`some CindyScript;\\`\\` to generate: \n\n\\`\\`\\`html\n\n\\`\\`\\`\n`","pinned":false,"hidden":false,"mode":"ojs"},{"id":537,"value":"cdy = id => (strings, ...exps) =>\n html``","pinned":true,"hidden":false,"mode":"ojs"},{"id":1196,"value":"md`Now that this notebook is published, you can use the following [Observable \\`import\\` statement](https://beta.observablehq.com/@mbostock/introduction-to-imports):\n\n\\`\\`\\`js\nimport {CindyJS, CindyJScss, cdy} from '@bryangingechen/hello-cindyjs'\n\\`\\`\\`\n\nYou can also import canvases created by CindyJS from notebooks, though it's a bit unwieldy since you have to import and include the CindyScript and CindyJS objects as well. See [this notebook](/@bryangingechen/cindyjs-import-example) for an example.`","pinned":false,"hidden":false,"mode":"ojs"},{"id":811,"value":"md`## [Julia set example](https://cindyjs.org/gallery/main/JuliaConjugated/) in detail`","pinned":false,"hidden":false,"mode":"ojs"},{"id":814,"value":"$32","pinned":false,"hidden":false,"mode":"ojs"},{"id":744,"value":"juliaCindy = {\n // the following lines mark those cells as dependencies of this one in the Observable runtime\n cdyJuliaInit;\n cdyJuliaDraw;\n juliaCanvas;\n const gslp = [];\n const cdy = CindyJS({\n scripts: \"julia*\",\n geometry: gslp,\n animation: { autoplay: true },\n ports: [\n {\n id: \"JuliaCanvas\",\n width: width,\n height: Math.floor(width / 2),\n transform: [{ visibleRect: [-1.5, -1.5, 6, 1.5] }]\n }\n ]\n });\n cdy.startup();\n invalidation.then(() => cdy.shutdown());\n return cdy;\n}","pinned":true,"hidden":false,"mode":"ojs"},{"id":834,"value":"md`The next two cells consist of the CindyScript ([reference wiki](https://doc.cinderella.de/tiki-index.php?page=CindyScript)) (using CindyGL ([tutorial](https://cindyjs.org/docs/cindygltutorial/))) which are found and interpreted by CindyJS. \n\nNote that the \\`id\\`s of their \\`