Enums also come with an underlying type, meaning that each constant inside the curly brackets has an associated value. The default underlying type is int and starts at 0, just like arrays, with each sequential constant getting the next highest number.
Not all types are created equal—underlying types for enumerations are limited to byte, sbyte, short, ushort, int, uint, long, and ulong. These are called integral types, which are used to specify the size of numeric values that a variable can store.
This is a bit advanced for this book, but you'll be using int in most cases. More information on these types can be found here: https://docs.microsoft.com/en-us/dotnet/csharp/language-reference/keywords/enum.
For example, our enum PlayerAction values right now are listed as follows, even though they aren't explicitly written out:
enum PlayerAction { Attack = 0, Defend = 1, Flee = 2 };
There's no rule that says underlying values need to start...