Gray Hole (GH) is non-sophisticated Math authoring tool. It is released under GNU license . Copyright (C) 2007 Konstantin Kirillov. This screenshot gives brief idea about GH: GH user who authores new Models/Problems (called below Authorer) can add "Models" to the set of already existing "Models". For each Model, Authorer can add set of Problems which are specific instances of the Model set by specifying Model's parameters. After completing authoring, any user (called below User) can read and run Problems and modify their parameters and rerun. The typical scenario of exploring GH is for Teacher-Authorer and Students-Users. To add new Model, Authorer needs to add source code for this problem. Therefore, for full use, Microsoft Visual Basic 4 or higher is required. If VB4 is missed, GH still can be used but no new Model can be added to executable file, only Problems can be added for existing Models. Authorer can create/add Model and Problem descriptions in html. Editing this descriptions called "Article Editing" in GH. Use "Display" buttons to display them in GH GUI. To run specific Problem, use "Run" button. GH is no longer in development. GH is far from being convenient and fully completed/tested project. GH is released in hope still being useful. Likely, other platforms/approaches like Java will require less work to implement a Model. No responsibility is accepted for accidental data damage caused/related to this program. To report malfunctions/suggestions/modifications, email to b e a v e r s c r i p t [ a t ] l a n d k e y [ d o t ] n e t (Replace [ a t ] with @, [ d o t ] with ".", remove blanks). Download Source Code and Executable Following are screenshots from GH. Thank you for your attention to GH.