General

C++ Tutorial eBooks
- C++ Language Tutorial
- Practical C++ Programming
- Lecture Slides for Programming in C++
- Learn C++ programming language
- A Complete Guide to Programming in C++ 

Half-Life

Goldsrc
- Half-Life C++
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Mods
- Ricochet
- Natural Selection
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Bots
- HPB bot
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Source Codes
- Half-Life 1 Engine download
- Half-Life SDK v2.3 download
- Natural Selection Source Code download 

Half-Life 2

Source SDK 2013
- download package
- Source SDK 2013 Multiplayer