Working through Jeremy Gibson Bond's excellent "Introduction to Game Design, Prototyping, and Development (Third Edition)".
Chapter 20, Variable and Components, gives a useful overview of Unity GameObjects and their components.
It also enumerates several of the bizarre gotchas in Unity, including:
The constants in the Color class (like Color.red) don't follow the usual capitalization convention for constants (SCREAMING_SNAKE_CASE).
"Mesh Colliders can only collide with other Mesh Colliders if both of them have Convex set to true."
"For the position of a Collider component to move with its GameObject, the GameObject must have a RigidBody. Otherwise ... the Collider will not move ...the GameObject will appear to move across the screen, but ... the location of the Collider component will not be updated, and therefore the physical presence of the GameObject will remain in the same location."
The Inspector changes the spacing and capitalization of class and variable names when it displays them, so (e.g.) damageState is displayed as Damage State.
This reminds me of heavy historical wargames that have all kinds of special rules like, "You can have up to three armor units in a city hex, except for hex 2334, which is limited to two armor units until the June 1943 turn (when, historically, the sewage plant exploded)."