Microgames from unity- Kart, FPS, platformer
https://assetstore.unity.com/?q=Microgame&orderBy=0
Templates
https://assetstore.unity.com/templates
Systems
https://assetstore.unity.com/templates/systems
Unity Technologies
Lots of free kits
https://assetstore.unity.com/publishers/1
Unity game DEV Ditzel github repo
https://github.com/ditzel
Quaternions and 3D rotation explained interactively
Houdini Engine
Procedural assets
