- Advanced Level
- C
- C++
- Perl/XS
- Lisp family languages(Especially Emacs Lisp)
- Intermediate Level
- Golang
- Rust
- Python
- node.js, C++ native module, Rust native module
- TypeScript, JavaScript
- C#, Unity
- F#
- Java, Kotlin
- Objective-C, Objective-C++, Swift
- Dart
- assembly lanaguage(ARMv7, MIPS)
- Electron, Chromium
- Flutter
- OS
- Linux kernel
- FreeBSD kernel
- NetBSD kernel
- Windows application in C++
- macOS application in Objective-C, Objective-C++
- Android
- iOS
- Practices
- Test Driven Development
- Object Oriented Programming