Flog is a Ruby code complexity analyzer that calculates an ABC (assignments, branches, conditionals) complexity metric with Ruby-specific enhancements. It processes Ruby source files to identify complex/tortured code that is difficult to test and maintain. The system consists of a core Flog library that performs the analysis, a CLI interface for command-line usage, a Rake task for integration with build systems, and a plugin system for extensibility. The architecture cleanly separates concerns: the Flog class handles AST processing and scoring, FlogCLI manages option parsing and file discovery, and FlogTask provides Rake integration. Recent versions have switched to using the prism parser for improved performance while maintaining backward compatibility with a --legacy flag for RubyParser.