Java Applets (not favored these days)
The Java applets can run in a variety of configurations (with different menus, different menu items, different logical systems, etc.). Which configuration a running instance uses depends on how they are launched, and preferences that the User (or Instructor) chooses. The examples shown here are mostly running Introduction and Elimination rules (Gentzen sequent calculus adapted to a friendly presentation).
Examples of Applets (not favored these days)
Most modern web browsers (say those produced after 2015) will not run Java Applets, even if you have Java installed and enabled . (So, as might be said in the US 'You're SOL'). The work around is just to download the full application Deriver.jar and run that off your desktop— it can do everything the applets can and more besides).
[Applets can take 30 seconds to launch on recent Apple Macintoshes, but they launch in perhaps 10 seconds on most other machines]
Example of Proof Applet
Example of Tree Applet
Example of Semantics Applet
Example of Symbolization Applet
Example of Modal Trees Applet
Example of Modal Truth Tables Applet
Example of Reading a Counter Example from a Tree
Example of Examination Applet
Example of Lambda Applet
Example of Endorse-Deny Applet
These are Java Applets. We are tended not to favor them going forward as it is unclear that they will run quickly and easily on the various computing devices.