Here is threed a simple 3D viewer
(need Java 8 JVM). The idea was to morph this into a 3D puzzle.
The X Manual Page is written for the X version but may be useful
to understanding the Java program. You can download the jar file
(preserve the .jar extension), and then it can be run as an
application like "java -jar ThreedApp.jar". (The puzzles used to be
able to run as applets but browsers and Oracle have dropped support.)