The toplevel runs off the UI thread, so a long computation never freezes the page. A Web Worker has no DOM though, so code typed here cannot touch the page (Dom_html, Graphics, ...); the stdlib and Lwt work.
| Enter | Submit code |
| Shift/Ctrl + Enter | Newline |
| Up / Down | Browse history |
| Ctrl + L | Clear output |
| Ctrl + K | Reset toplevel |
| Tab | Indent code |