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Creating interactive learning interfaces
 at Khan Academy Ben Alpert and Pamela Fox

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Constraints
 are liberating.

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“khan-exercises”

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randRange(5, 10) randRange(5, 10)
!

Bob has X apples...

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graphInit({ range: 10, scale: 20 }); ! plot(function(x) { return 2 * sin(x); }, [-10, 10]);

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Solid line Dashed line

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Too much power.

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“Perseus”

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What about pictures?

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For diagrams, we want… • Simple to create • Consistent look and feel • Flexibility to draw anything

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Diagrams turn into image files that any browser can render, but we save the source too.

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Constraining yourself can be liberating too.

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var MissionDashboard = React.createClass({ render: function() { return (
); } });

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“Falling into the“
 “pit of success” Jeff Atwood

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Unthematic announcement time.

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f ( x ) = Z 1 1 ˆ f ( ⇠ ) e 2 ⇡i⇠x d⇠

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• Used in production since last summer • Beautiful math typesetting • About 50x faster than MathJax • http://khan.github.io/KaTeX/

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Thanks.