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Apollonian circle packing
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<iframe 
    src="https://jsxgraph.org/share/iframe/apollonian-circle-packing" 
    style="border: 1px solid black; overflow: hidden; width: 550px; aspect-ratio: 55 / 65;" 
    name="JSXGraph example: Apollonian circle packing" 
    allowfullscreen
></iframe>
This code has to 
<div id="board-0-wrapper" class="jxgbox-wrapper " style="width: 100%; ">
   <div id="board-0" class="jxgbox" style="aspect-ratio: 1 / 1; width: 100%;" data-ar="1 / 1"></div>
</div>

<script type = "text/javascript"> 
    /*
    This example is licensed under a 
    Creative Commons Attribution 4.0 International License.
    https://creativecommons.org/licenses/by/4.0/
    
    Please note you have to mention 
    The Center of Mobile Learning with Digital Technology
    in the credits.
    */
    
    const BOARDID = 'board-0';

    var board = JXG.JSXGraph.initBoard(BOARDID, {
            boundingbox: [-2.5, 2.5, 2.5, -2.5],
            showNavigation: false,
            pan: { enabled: false },
            zoom: { enabled: false }
        }),
        solveQ2 = function(x1, x2, x3, off) {
            var a, b, c, d;
            a = 0.5;
            b = -(x1 + x2 + x3);
            c = x1 * x1 + x2 * x2 + x3 * x3 - 0.5 * (x1 + x2 + x3) * (x1 + x2 + x3) - off;
            d = b * b - 4 * a * c;
            if (Math.abs(d) < JXG.Math.eps) {
                d = 0.0;
            }
            return [(-b + Math.sqrt(d)) / (2.0 * a), (-b - Math.sqrt(d)) / (2.0 * a)];
        };
    
    var a = board.create('line', [[0, 0], [2, 0]], { straightFirst: false, straightLast: false, visible: false }),
        p0 = board.create('point', [0, 0], { name: '', visible: false }),
        p1 = board.create('glider', [1.3, 0, a], { name: 'drag me', showInfobox: false, label: { offset: [-20, 15] } }),
    
        b0 = -0.5,
        r1 = 2 - p1.X(),
        b1 = 1.0 / r1,
        r2 = (2.0 - r1),
        b2 = 1.0 / r2,
    
        p2 = board.create('point', [function() { return p1.X() - 2; }, 0], { name: '', visible: false }),
    
        c0 = board.create('circle', [p0, Math.abs(1.0 / b0)], { strokeWidth: 1, withLabel: false }),
        c1 = board.create('circle', [p1, function() { return 2 - p1.X(); }], { strokeWidth: 1, withLabel: false }),
        c2 = board.create('circle', [p2, function() { return p1.X(); }], { strokeWidth: 1, withLabel: false });
    
    c0.curvature = function() { return b0; }; // constant
    c1.curvature = function() { return 1 / (2 - p1.X()); };
    c2.curvature = function() { return 1 / (p1.X()); };
    
    var thirdCircleX = function() {
            var b0, b1, b2, x0, x1, x2, b3, bx3;
            b0 = c0.curvature();
            b1 = c1.curvature();
            b2 = c2.curvature();
            x0 = c0.midpoint.X();
            x1 = c1.midpoint.X();
            x2 = c2.midpoint.X();
    
            b3 = solveQ2(b0, b1, b2, 0);
            bx3 = solveQ2(b0 * x0, b1 * x1, b2 * x2, 2);
            return bx3[0] / b3[0];
        },
        thirdCircleY = function() {
            var b0, b1, b2, y0, y1, y2, b3, by3;
            b0 = c0.curvature();
            b1 = c1.curvature();
            b2 = c2.curvature();
            y0 = c0.midpoint.Y();
            y1 = c1.midpoint.Y();
            y2 = c2.midpoint.Y();
    
            b3 = solveQ2(b0, b1, b2, 0);
            by3 = solveQ2(b0 * y0, b1 * y1, b2 * y2, 2);
            return by3[0] / b3[0];
        },
        thirdCircleRadius = function() {
            var b0, b1, b2, b3, bx3, by3;
            b0 = c0.curvature();
            b1 = c1.curvature();
            b2 = c2.curvature();
            b3 = solveQ2(b0, b1, b2, 0);
            return 1.0 / b3[0];
        };
    
    var p3 = board.create('point', [thirdCircleX, thirdCircleY], { name: '', visible: false }),
        c3 = board.create('circle', [p3, thirdCircleRadius], { strokeWidth: 1, withLabel: false });
    
    c3.curvature = function() { return 1.0 / this.radius; };
    
    var otherCirc = function(circs, level) {
        var p, c, fx, fy, fr;
    
        if (level <= 0) {
            return;
        }
        fx = function() {
            var b = [],
                x = [],
                i;
            for (i = 0; i < 4; i++) {
                b[i] = circs[i].curvature();
                x[i] = circs[i].midpoint.X();
            }
    
            b[4] = 2 * (b[0] + b[1] + b[2]) - b[3];
            x[4] = (2 * (b[0] * x[0] + b[1] * x[1] + b[2] * x[2]) - b[3] * x[3]) / b[4];
            return x[4];
        };
        fy = function() {
            var b = [],
                y = [],
                i;
            for (i = 0; i < 4; i++) {
                b[i] = circs[i].curvature();
                y[i] = circs[i].midpoint.Y();
            }
    
            b[4] = 2 * (b[0] + b[1] + b[2]) - b[3];
            y[4] = (2 * (b[0] * y[0] + b[1] * y[1] + b[2] * y[2]) - b[3] * y[3]) / b[4];
            return y[4];
        };
        fr = function() {
            var b = [],
                i;
            for (i = 0; i < 4; i++) {
                b[i] = circs[i].curvature();
            }
            b[4] = 2 * (b[0] + b[1] + b[2]) - b[3];
            if (isNaN(b[4])) {
                return 1000.0;
            } else {
                return 1 / b[4];
            }
        };
        p = board.create('point', [fx, fy], { name: '', visible: false });
        c = board.create('circle', [p, fr], {
            strokeWidth: 1,
            fillColor: JXG.hsv2rgb((70 * level) % 360, 0.9, 1),
            highlightFillColor: JXG.hsv2rgb((70 * level) % 360, 0.9, 0.6),
            fillOpacity: 0.7,
            withLabel: false,
        });
        c.curvature = function() { return 1 / this.radius; };
    
        // Recursion
        otherCirc([circs[0], circs[1], c, circs[2]], level - 1);
        otherCirc([circs[0], circs[2], c, circs[1]], level - 1);
        otherCirc([circs[1], circs[2], c, circs[0]], level - 1);
        return c;
    };
    
    //-------------------------------------------------------
    var level = 3;
    otherCirc([c0, c1, c2, c3], level);
    otherCirc([c3, c1, c2, c0], level);
    otherCirc([c0, c2, c3, c1], level);
    otherCirc([c0, c1, c3, c2], level);
 </script> 
/*
This example is licensed under a 
Creative Commons Attribution 4.0 International License.
https://creativecommons.org/licenses/by/4.0/

Please note you have to mention 
The Center of Mobile Learning with Digital Technology
in the credits.
*/

const BOARDID = 'your_div_id'; // Insert your id here!

var board = JXG.JSXGraph.initBoard(BOARDID, {
        boundingbox: [-2.5, 2.5, 2.5, -2.5],
        showNavigation: false,
        pan: { enabled: false },
        zoom: { enabled: false }
    }),
    solveQ2 = function(x1, x2, x3, off) {
        var a, b, c, d;
        a = 0.5;
        b = -(x1 + x2 + x3);
        c = x1 * x1 + x2 * x2 + x3 * x3 - 0.5 * (x1 + x2 + x3) * (x1 + x2 + x3) - off;
        d = b * b - 4 * a * c;
        if (Math.abs(d) < JXG.Math.eps) {
            d = 0.0;
        }
        return [(-b + Math.sqrt(d)) / (2.0 * a), (-b - Math.sqrt(d)) / (2.0 * a)];
    };

var a = board.create('line', [[0, 0], [2, 0]], { straightFirst: false, straightLast: false, visible: false }),
    p0 = board.create('point', [0, 0], { name: '', visible: false }),
    p1 = board.create('glider', [1.3, 0, a], { name: 'drag me', showInfobox: false, label: { offset: [-20, 15] } }),

    b0 = -0.5,
    r1 = 2 - p1.X(),
    b1 = 1.0 / r1,
    r2 = (2.0 - r1),
    b2 = 1.0 / r2,

    p2 = board.create('point', [function() { return p1.X() - 2; }, 0], { name: '', visible: false }),

    c0 = board.create('circle', [p0, Math.abs(1.0 / b0)], { strokeWidth: 1, withLabel: false }),
    c1 = board.create('circle', [p1, function() { return 2 - p1.X(); }], { strokeWidth: 1, withLabel: false }),
    c2 = board.create('circle', [p2, function() { return p1.X(); }], { strokeWidth: 1, withLabel: false });

c0.curvature = function() { return b0; }; // constant
c1.curvature = function() { return 1 / (2 - p1.X()); };
c2.curvature = function() { return 1 / (p1.X()); };

var thirdCircleX = function() {
        var b0, b1, b2, x0, x1, x2, b3, bx3;
        b0 = c0.curvature();
        b1 = c1.curvature();
        b2 = c2.curvature();
        x0 = c0.midpoint.X();
        x1 = c1.midpoint.X();
        x2 = c2.midpoint.X();

        b3 = solveQ2(b0, b1, b2, 0);
        bx3 = solveQ2(b0 * x0, b1 * x1, b2 * x2, 2);
        return bx3[0] / b3[0];
    },
    thirdCircleY = function() {
        var b0, b1, b2, y0, y1, y2, b3, by3;
        b0 = c0.curvature();
        b1 = c1.curvature();
        b2 = c2.curvature();
        y0 = c0.midpoint.Y();
        y1 = c1.midpoint.Y();
        y2 = c2.midpoint.Y();

        b3 = solveQ2(b0, b1, b2, 0);
        by3 = solveQ2(b0 * y0, b1 * y1, b2 * y2, 2);
        return by3[0] / b3[0];
    },
    thirdCircleRadius = function() {
        var b0, b1, b2, b3, bx3, by3;
        b0 = c0.curvature();
        b1 = c1.curvature();
        b2 = c2.curvature();
        b3 = solveQ2(b0, b1, b2, 0);
        return 1.0 / b3[0];
    };

var p3 = board.create('point', [thirdCircleX, thirdCircleY], { name: '', visible: false }),
    c3 = board.create('circle', [p3, thirdCircleRadius], { strokeWidth: 1, withLabel: false });

c3.curvature = function() { return 1.0 / this.radius; };

var otherCirc = function(circs, level) {
    var p, c, fx, fy, fr;

    if (level <= 0) {
        return;
    }
    fx = function() {
        var b = [],
            x = [],
            i;
        for (i = 0; i < 4; i++) {
            b[i] = circs[i].curvature();
            x[i] = circs[i].midpoint.X();
        }

        b[4] = 2 * (b[0] + b[1] + b[2]) - b[3];
        x[4] = (2 * (b[0] * x[0] + b[1] * x[1] + b[2] * x[2]) - b[3] * x[3]) / b[4];
        return x[4];
    };
    fy = function() {
        var b = [],
            y = [],
            i;
        for (i = 0; i < 4; i++) {
            b[i] = circs[i].curvature();
            y[i] = circs[i].midpoint.Y();
        }

        b[4] = 2 * (b[0] + b[1] + b[2]) - b[3];
        y[4] = (2 * (b[0] * y[0] + b[1] * y[1] + b[2] * y[2]) - b[3] * y[3]) / b[4];
        return y[4];
    };
    fr = function() {
        var b = [],
            i;
        for (i = 0; i < 4; i++) {
            b[i] = circs[i].curvature();
        }
        b[4] = 2 * (b[0] + b[1] + b[2]) - b[3];
        if (isNaN(b[4])) {
            return 1000.0;
        } else {
            return 1 / b[4];
        }
    };
    p = board.create('point', [fx, fy], { name: '', visible: false });
    c = board.create('circle', [p, fr], {
        strokeWidth: 1,
        fillColor: JXG.hsv2rgb((70 * level) % 360, 0.9, 1),
        highlightFillColor: JXG.hsv2rgb((70 * level) % 360, 0.9, 0.6),
        fillOpacity: 0.7,
        withLabel: false,
    });
    c.curvature = function() { return 1 / this.radius; };

    // Recursion
    otherCirc([circs[0], circs[1], c, circs[2]], level - 1);
    otherCirc([circs[0], circs[2], c, circs[1]], level - 1);
    otherCirc([circs[1], circs[2], c, circs[0]], level - 1);
    return c;
};

//-------------------------------------------------------
var level = 3;
otherCirc([c0, c1, c2, c3], level);
otherCirc([c3, c1, c2, c0], level);
otherCirc([c0, c2, c3, c1], level);
otherCirc([c0, c1, c3, c2], level);
<jsxgraph width="100%" aspect-ratio="1 / 1" title="Apollonian circle packing" description="This construction was copied from JSXGraph examples database: BTW HERE SHOULD BE A GENERATED LINKuseGlobalJS="false">
   /*
   This example is licensed under a 
   Creative Commons Attribution 4.0 International License.
   https://creativecommons.org/licenses/by/4.0/
   
   Please note you have to mention 
   The Center of Mobile Learning with Digital Technology
   in the credits.
   */
   
   var board = JXG.JSXGraph.initBoard(BOARDID, {
           boundingbox: [-2.5, 2.5, 2.5, -2.5],
           showNavigation: false,
           pan: { enabled: false },
           zoom: { enabled: false }
       }),
       solveQ2 = function(x1, x2, x3, off) {
           var a, b, c, d;
           a = 0.5;
           b = -(x1 + x2 + x3);
           c = x1 * x1 + x2 * x2 + x3 * x3 - 0.5 * (x1 + x2 + x3) * (x1 + x2 + x3) - off;
           d = b * b - 4 * a * c;
           if (Math.abs(d) < JXG.Math.eps) {
               d = 0.0;
           }
           return [(-b + Math.sqrt(d)) / (2.0 * a), (-b - Math.sqrt(d)) / (2.0 * a)];
       };
   
   var a = board.create('line', [[0, 0], [2, 0]], { straightFirst: false, straightLast: false, visible: false }),
       p0 = board.create('point', [0, 0], { name: '', visible: false }),
       p1 = board.create('glider', [1.3, 0, a], { name: 'drag me', showInfobox: false, label: { offset: [-20, 15] } }),
   
       b0 = -0.5,
       r1 = 2 - p1.X(),
       b1 = 1.0 / r1,
       r2 = (2.0 - r1),
       b2 = 1.0 / r2,
   
       p2 = board.create('point', [function() { return p1.X() - 2; }, 0], { name: '', visible: false }),
   
       c0 = board.create('circle', [p0, Math.abs(1.0 / b0)], { strokeWidth: 1, withLabel: false }),
       c1 = board.create('circle', [p1, function() { return 2 - p1.X(); }], { strokeWidth: 1, withLabel: false }),
       c2 = board.create('circle', [p2, function() { return p1.X(); }], { strokeWidth: 1, withLabel: false });
   
   c0.curvature = function() { return b0; }; // constant
   c1.curvature = function() { return 1 / (2 - p1.X()); };
   c2.curvature = function() { return 1 / (p1.X()); };
   
   var thirdCircleX = function() {
           var b0, b1, b2, x0, x1, x2, b3, bx3;
           b0 = c0.curvature();
           b1 = c1.curvature();
           b2 = c2.curvature();
           x0 = c0.midpoint.X();
           x1 = c1.midpoint.X();
           x2 = c2.midpoint.X();
   
           b3 = solveQ2(b0, b1, b2, 0);
           bx3 = solveQ2(b0 * x0, b1 * x1, b2 * x2, 2);
           return bx3[0] / b3[0];
       },
       thirdCircleY = function() {
           var b0, b1, b2, y0, y1, y2, b3, by3;
           b0 = c0.curvature();
           b1 = c1.curvature();
           b2 = c2.curvature();
           y0 = c0.midpoint.Y();
           y1 = c1.midpoint.Y();
           y2 = c2.midpoint.Y();
   
           b3 = solveQ2(b0, b1, b2, 0);
           by3 = solveQ2(b0 * y0, b1 * y1, b2 * y2, 2);
           return by3[0] / b3[0];
       },
       thirdCircleRadius = function() {
           var b0, b1, b2, b3, bx3, by3;
           b0 = c0.curvature();
           b1 = c1.curvature();
           b2 = c2.curvature();
           b3 = solveQ2(b0, b1, b2, 0);
           return 1.0 / b3[0];
       };
   
   var p3 = board.create('point', [thirdCircleX, thirdCircleY], { name: '', visible: false }),
       c3 = board.create('circle', [p3, thirdCircleRadius], { strokeWidth: 1, withLabel: false });
   
   c3.curvature = function() { return 1.0 / this.radius; };
   
   var otherCirc = function(circs, level) {
       var p, c, fx, fy, fr;
   
       if (level <= 0) {
           return;
       }
       fx = function() {
           var b = [],
               x = [],
               i;
           for (i = 0; i < 4; i++) {
               b[i] = circs[i].curvature();
               x[i] = circs[i].midpoint.X();
           }
   
           b[4] = 2 * (b[0] + b[1] + b[2]) - b[3];
           x[4] = (2 * (b[0] * x[0] + b[1] * x[1] + b[2] * x[2]) - b[3] * x[3]) / b[4];
           return x[4];
       };
       fy = function() {
           var b = [],
               y = [],
               i;
           for (i = 0; i < 4; i++) {
               b[i] = circs[i].curvature();
               y[i] = circs[i].midpoint.Y();
           }
   
           b[4] = 2 * (b[0] + b[1] + b[2]) - b[3];
           y[4] = (2 * (b[0] * y[0] + b[1] * y[1] + b[2] * y[2]) - b[3] * y[3]) / b[4];
           return y[4];
       };
       fr = function() {
           var b = [],
               i;
           for (i = 0; i < 4; i++) {
               b[i] = circs[i].curvature();
           }
           b[4] = 2 * (b[0] + b[1] + b[2]) - b[3];
           if (isNaN(b[4])) {
               return 1000.0;
           } else {
               return 1 / b[4];
           }
       };
       p = board.create('point', [fx, fy], { name: '', visible: false });
       c = board.create('circle', [p, fr], {
           strokeWidth: 1,
           fillColor: JXG.hsv2rgb((70 * level) % 360, 0.9, 1),
           highlightFillColor: JXG.hsv2rgb((70 * level) % 360, 0.9, 0.6),
           fillOpacity: 0.7,
           withLabel: false,
       });
       c.curvature = function() { return 1 / this.radius; };
   
       // Recursion
       otherCirc([circs[0], circs[1], c, circs[2]], level - 1);
       otherCirc([circs[0], circs[2], c, circs[1]], level - 1);
       otherCirc([circs[1], circs[2], c, circs[0]], level - 1);
       return c;
   };
   
   //-------------------------------------------------------
   var level = 3;
   otherCirc([c0, c1, c2, c3], level);
   otherCirc([c3, c1, c2, c0], level);
   otherCirc([c0, c2, c3, c1], level);
   otherCirc([c0, c1, c3, c2], level);
</jsxgraph>

Apollonian circle packing

Euclidean
Geometry
__References__ - [https://www.ams.org/featurecolumn/archive/kissing.html](https://www.ams.org/featurecolumn/archive/kissing.html) - Jeffrey C. Lagarias, Colin L. Mallows, Allan R. Wilks: Beyond the Descartes circle theorem - [https://en.wikipedia.org/wiki/Apollonian_gasket](https://en.wikipedia.org/wiki/Apollonian_gasket) - Weisstein, Eric W. ["Apollonian Gasket."](https://mathworld.wolfram.com/ApollonianGasket.html) From MathWorld - A Wolfram Web Resource - Weisstein, Eric W. ["Soddy Circles."](https://mathworld.wolfram.com/SoddyCircles.html) From MathWorld - A Wolfram Web Resource 
// Define the id of your board in BOARDID

var board = JXG.JSXGraph.initBoard(BOARDID, {
        boundingbox: [-2.5, 2.5, 2.5, -2.5],
        showNavigation: false,
        pan: { enabled: false },
        zoom: { enabled: false }
    }),
    solveQ2 = function(x1, x2, x3, off) {
        var a, b, c, d;
        a = 0.5;
        b = -(x1 + x2 + x3);
        c = x1 * x1 + x2 * x2 + x3 * x3 - 0.5 * (x1 + x2 + x3) * (x1 + x2 + x3) - off;
        d = b * b - 4 * a * c;
        if (Math.abs(d) < JXG.Math.eps) {
            d = 0.0;
        }
        return [(-b + Math.sqrt(d)) / (2.0 * a), (-b - Math.sqrt(d)) / (2.0 * a)];
    };

var a = board.create('line', [[0, 0], [2, 0]], { straightFirst: false, straightLast: false, visible: false }),
    p0 = board.create('point', [0, 0], { name: '', visible: false }),
    p1 = board.create('glider', [1.3, 0, a], { name: 'drag me', showInfobox: false, label: { offset: [-20, 15] } }),

    b0 = -0.5,
    r1 = 2 - p1.X(),
    b1 = 1.0 / r1,
    r2 = (2.0 - r1),
    b2 = 1.0 / r2,

    p2 = board.create('point', [function() { return p1.X() - 2; }, 0], { name: '', visible: false }),

    c0 = board.create('circle', [p0, Math.abs(1.0 / b0)], { strokeWidth: 1, withLabel: false }),
    c1 = board.create('circle', [p1, function() { return 2 - p1.X(); }], { strokeWidth: 1, withLabel: false }),
    c2 = board.create('circle', [p2, function() { return p1.X(); }], { strokeWidth: 1, withLabel: false });

c0.curvature = function() { return b0; }; // constant
c1.curvature = function() { return 1 / (2 - p1.X()); };
c2.curvature = function() { return 1 / (p1.X()); };

var thirdCircleX = function() {
        var b0, b1, b2, x0, x1, x2, b3, bx3;
        b0 = c0.curvature();
        b1 = c1.curvature();
        b2 = c2.curvature();
        x0 = c0.midpoint.X();
        x1 = c1.midpoint.X();
        x2 = c2.midpoint.X();

        b3 = solveQ2(b0, b1, b2, 0);
        bx3 = solveQ2(b0 * x0, b1 * x1, b2 * x2, 2);
        return bx3[0] / b3[0];
    },
    thirdCircleY = function() {
        var b0, b1, b2, y0, y1, y2, b3, by3;
        b0 = c0.curvature();
        b1 = c1.curvature();
        b2 = c2.curvature();
        y0 = c0.midpoint.Y();
        y1 = c1.midpoint.Y();
        y2 = c2.midpoint.Y();

        b3 = solveQ2(b0, b1, b2, 0);
        by3 = solveQ2(b0 * y0, b1 * y1, b2 * y2, 2);
        return by3[0] / b3[0];
    },
    thirdCircleRadius = function() {
        var b0, b1, b2, b3, bx3, by3;
        b0 = c0.curvature();
        b1 = c1.curvature();
        b2 = c2.curvature();
        b3 = solveQ2(b0, b1, b2, 0);
        return 1.0 / b3[0];
    };

var p3 = board.create('point', [thirdCircleX, thirdCircleY], { name: '', visible: false }),
    c3 = board.create('circle', [p3, thirdCircleRadius], { strokeWidth: 1, withLabel: false });

c3.curvature = function() { return 1.0 / this.radius; };

var otherCirc = function(circs, level) {
    var p, c, fx, fy, fr;

    if (level <= 0) {
        return;
    }
    fx = function() {
        var b = [],
            x = [],
            i;
        for (i = 0; i < 4; i++) {
            b[i] = circs[i].curvature();
            x[i] = circs[i].midpoint.X();
        }

        b[4] = 2 * (b[0] + b[1] + b[2]) - b[3];
        x[4] = (2 * (b[0] * x[0] + b[1] * x[1] + b[2] * x[2]) - b[3] * x[3]) / b[4];
        return x[4];
    };
    fy = function() {
        var b = [],
            y = [],
            i;
        for (i = 0; i < 4; i++) {
            b[i] = circs[i].curvature();
            y[i] = circs[i].midpoint.Y();
        }

        b[4] = 2 * (b[0] + b[1] + b[2]) - b[3];
        y[4] = (2 * (b[0] * y[0] + b[1] * y[1] + b[2] * y[2]) - b[3] * y[3]) / b[4];
        return y[4];
    };
    fr = function() {
        var b = [],
            i;
        for (i = 0; i < 4; i++) {
            b[i] = circs[i].curvature();
        }
        b[4] = 2 * (b[0] + b[1] + b[2]) - b[3];
        if (isNaN(b[4])) {
            return 1000.0;
        } else {
            return 1 / b[4];
        }
    };
    p = board.create('point', [fx, fy], { name: '', visible: false });
    c = board.create('circle', [p, fr], {
        strokeWidth: 1,
        fillColor: JXG.hsv2rgb((70 * level) % 360, 0.9, 1),
        highlightFillColor: JXG.hsv2rgb((70 * level) % 360, 0.9, 0.6),
        fillOpacity: 0.7,
        withLabel: false,
    });
    c.curvature = function() { return 1 / this.radius; };

    // Recursion
    otherCirc([circs[0], circs[1], c, circs[2]], level - 1);
    otherCirc([circs[0], circs[2], c, circs[1]], level - 1);
    otherCirc([circs[1], circs[2], c, circs[0]], level - 1);
    return c;
};

//-------------------------------------------------------
var level = 3;
otherCirc([c0, c1, c2, c3], level);
otherCirc([c3, c1, c2, c0], level);
otherCirc([c0, c2, c3, c1], level);
otherCirc([c0, c1, c3, c2], level);

license

This example is licensed under a Creative Commons Attribution 4.0 International License.
Please note you have to mention The Center of Mobile Learning with Digital Technology in the credits.