If anyone is wondering, the interactive calculator is done using Tangle (http://worrydream.com/Tangle/ http://worrydream.com/Tangle/) made by Bret Victor (most

If anyone is wondering, the interactive calculator is done using Tangle (http://worrydream.com/Tangle/ http://worrydream.com/Tangle/) made by Bret Victor (most recently of http://worrydream.com/#!/LadderOfAbstraction http://worrydream.com/#!/LadderOfAbstraction fame). Good to see more examples of it in the wild.