From the beginning, Sudoku Sensei was intended to become a program with Graphical User Interface. Though, the first versions were just the core of that: a sudoku logic explainer engine. That is, a library capable of solving sudokus just like humans do.

The engine solves sudokus by applying complex logical rules a few times, instead of applying simpler rules (like guessing and backtracking) many many times. These complex logical rules are exactly the same ones that people use with paper and pen.

In the first versions of Sudoku Sensei, the engine is accompanied by several command line demo programs. These illustrate how to use the engine and allow creating, solving and explaining a wide variety of sudoku problems.

The engine-only versions are still maintained. They can be very useful for creating in a row hundreds of sudoku problems graded by difficulty and in HTML format, ready for printing and playing with paper and pen.