The Numbiano Classroom

Safari silences most sites by default. With a tool open, choose Safari → Settings for this website and set Auto-Play to Allow All Auto-Play. Chrome needs nothing. Each tool prints its own audio state in the bottom corner, so if that reads a level above zero the sound is being made and it is the browser holding it back.

On an iPad, add this page to the Home Screen: in Safari, press Share, then Add to Home Screen. It opens full screen with the Numbiano icon, and every tool is a tap away. On a Chromebook, Chrome's menu can install it the same way.