How to check directory trees made available to proot'ed applications?
  BW_BROWSER_PATH=find ./browser-wrapper /dev
  BW_BROWSER_PATH=bash ./browser-wrapper -c "find /dev /home -maxdepth 3 | xargs ls -aldh"

How to quickly find a Flash application since they tend to disappear?
  Look for "Flash sample clock", it should lead you to
    https://www.adobe.com/devnet/actionscript/samples/time_2.html
  Of course, other samples are available on
    https://www.adobe.com/devnet/actionscript/samples.html

How to quickly find a webGL demo?
  "WebGL Samples" looks like the right place, e.g.:
     http://webglsamples.org/aquarium/aquarium.html
  Other demos:
    http://nouvellevague.ultranoir.com/
    http://madebyevan.com/webgl-water/
    http://www.randelshofer.ch/webgl/rubikscube/
    http://www.webglearth.com/

How to quickly find a Java applet since, well, you know.
  Looking for "java applet sample" should lead you to
    https://docs.oracle.com/javase/tutorial/deployment/applet/examplesIndex.html