In this 10 mins GameDev tips we are going to explore Quaternions in an intuitive way. Don't expect deep math derivations. However after watching this video you should have a good mental picture on how they could help you dealing with rotations and orientations in your game projects. I will start by describing euler angles and their issues following by a visual example of how quaternions works (using blender). Then we are going to see different applications of them in C# using unity.
Quaternions on wikipedia: https://www.wikiwand.com/en/Quaternion
Complex numbers on wikipedia: https://www.wikiwand.com/en/Complex_number
3BlueOneBrown Visualizing quaternions: https://www.youtube.com/watch?v=d4EgbgTm0Bg
Quaternions for computer graphics - J.Vince: https://www.amazon.com/Quaternions-Computer-Graphics-John-Vince/dp/0857297597
Ken Joy lecture: https://www.youtube.com/watch?v=mHVwd8gYLnI
Unity Quaternions doc: https://docs.unity3d.com/ScriptReference/Quaternion.html
Godot Quaternions doc: https://docs.godotengine.org/en/stable/classes/class_quat.html