ZeBadger has created several virtual machines with Windows XP, Firefox and Shockwave preconfigured to work. You will need to install a SPICE client like virt-viewer and message ZeBadger on Discord so he can allocate one of the machines to you. You will receive a username, password and two-factor authentication code.
Once you have done the above:
Tip: If your mouse/keyboard gets stuck inside the VM, use CTRL+ALT+r to release it.
Cribbed from the pinned post on the Discord channel and input from moosic -thanks!
Download and install the 32-bit version of Basilisk (unfortunately, this is no longer maintained, but it still works)
The latest available installer is http://archive.palemoon.org/basilisk/basilisk-20201125140449.win32.installer.exe
Other versions available here: http://archive.palemoon.org/basilisk/
Install Shockwave available from The Internet Archive sw_lic_full_installer.msi or sw_lic_full_installer.exe
When you try to play, make sure that you visit this URL https://isketch.net/isketch.shtml
See this Reddit post
Note that it's probably a really good idea to then go into the Chrome plug-in settings and only allow IE Tab access to https://www.isketch.net/