General:
* Algorithms
* Data Structures
* Design Patterns
* ESRI/GIS/Spatial Data
* Health Tech
* HL7
* Sports Tech
Mobile Development:
* iOS (Objective-C & Swift)
* Android (Java & Kotlin)
* Xamarin
* Flutter
* WindowsMobile & WindowsPhone
Desktop Development:
* C# (from 2.0 to .NET Core, WinForm, XAML, WPF, UWP)
* C++ (MFC, Multi-platform with Qt)
* Java
Web Development:
* ReactJS
* C# (Pre-MVC, MVC, WebAPI REST/SOAP, including .NET Core)
* C++ backend
* Java backend (including Springs)
* PHP (raw and frameworks)
* Django
* HTML/CSS/JS (including common frameworks)