Mirrored from Sudopedia, the Free Sudoku Reference Guide
Sudoku Explainer is one of the Sudoku Programs. The solving techniques that are implemented in Sudoku Explainer seem somewhat old-school: the most advanced techniques are heavy on Forcing Chains and Forcing Nets, often the type that tests for contradictions. The more recently developed ALS techniques do not appear in Sudoku Explainer.
The difficulty indicator of Sudoku Explainer is often used by the people who accept the regular use of Contradiction Nets. A difficulty level of 9.0, commonly seen in Sudoku Forums as "SE 9.0", would be extremely difficult.