I’m preparing an internal workshop entirely based on Kotlin Koans and I’m having a really bad experience with the online version - in some cases the Run button just does nothing. The browser console displays the following error:

Uncaught TypeError: Cannot read property 'execute' of null
    at Object.onRun (main.js:148)
    at main.js:148
    at Object.<anonymous> (main.js:132)
    at p (main.js:132)
    at main.js:132
    at C (main.js:132)
    at O (main.js:132)
    at A (main.js:132)
    at S (main.js:132)
    at L (main.js:132)

I’d say IDE will be a good bet

Our web-team says it should be this one: https://youtrack.jetbrains.com/issue/KT-29473. You are welcome to describe your particular case in the issue 🙂