What software was used to make this demo in Kolibri

I have been checking Kolibri demo at https://kolibridemo.learningequality.org/learn/#/197934f144305350b5820c7c4dd8e194/recommended/25ce58b71e49533198ca31fad5a04f50
and was wondering what software was used to make this interactive demo

Hi @alenguav,

PhET simulations are interactive HTML5 apps. You can see the original Forces and Motion sim here, and the code is on GitHub.