// Feedback from code review:

// pushdown_automata.go:
// 1. The BuildGraph function is quite long and could be split into smaller, more focused functions
// 2. Consider using constants instead of magic runes like rune(-1) for sentinel values
// 3. The state machine transitions could be defined more declaratively, perhaps in a config
// 4. The stringInvalidRunes list needs to handle escape sequences properly
// 5. The graph building could be optimized to avoid duplicate nodes/transitions
// 6. Consider adding validation for max nesting depth of braces/brackets
// 7. The CreateMask function is doing a lot - could be split into smaller pieces
// 8. isRuneValid has a "garbage interface" per TODO - needs cleaner design

// pushdown_runner.go:
// 1. The Apply method has a lot of duplicated logic around EOS handling
// 2. The UpdateState method could use more granular error messages
// 3. The braceStack validation could be moved to a separate validator
// 4. Consider adding max length limits for strings/numbers
// 5. The stateCounter isn't being used effectively yet
// 6. Need to add penalties for staying in same state too long
// 7. The maskLogits function could be optimized to avoid allocations
// 8. Missing proper cleanup/reset functionality
// 9. Error handling could be more consistent throughout
// 10. Consider adding debug logging levels instead of raw fmt.Println

// General improvements needed:
// - More comprehensive testing, especially edge cases
// - Better documentation of state machine transitions
// - Performance optimization for large inputs
// - Memory usage optimization for the graph structure
// - Cleaner interfaces between components
// - More robust error handling and recovery