ThingLab [2, 3] adopted many of the ideas in Sketchpad, and combined them with the extensibility and object-oriented techniques of the Smalltalk programming language .
In addition to its geometric applications, Sketchpad was used for simulating mechanical linkages, while ThingLab was used for simulating electrical circuits, highway bridges, and other physical objects.
Both ThingLab and Animus have been used in user-interface applications.
The DeltaBlue algorithm is currently being used in ThingLab II [13, 29], a user-interface construction kit using constraints, and Voyeur , a parallel program visualization and debugging project at the University of Washington.
ThingLab II is an object-oriented, interactive constraint programming system implemented in Smalltalk-80.
We have developed such a mechanism  to allow large user interfaces to be built with ThingLab II.
In ThingLab II, the user-manipulable entities are collections of objects known as Things.
Modules in ThingLab II were inspired by the components of Ariel and Fabrik , and by the Object Definer  from the original ThingLab.
Graphically defining new building blocks in ThingLab. Human-Comput.
The programming language aspects of ThingLab, a constraint-oriented simulation laboratory.