Programming language * self compiling compiler (self-hosting?). * self interpreter interpreter (metacircular evaluator) [from scratch. no parser generator or

Programming language * self compiling compiler (self-hosting?). * self interpreter interpreter (metacircular evaluator) [from scratch. no parser generator or backends like LLVM, or tools like that, as they hide much info and insight] Testing * Fuzzer (for testing, e.g. programming language implementation)