Top-level
=========

A ZScript file can have one of several things at the top level of the file:

- Class definitions
- Structure definitions
- Enumeration definitions
- Constant definitions
- Include directives

Class definitions
=================

A class definition starts with a class header, followed by an opening brace, class data and a closing brace. Alternatively, you can follow the class header with a semicolon and the rest of the file will be considered class data.

Class headers
-------------

The class header is formed as such:

```cs
   class Name [: BaseClass] [Class flags...]
```

Class flags include:

| Flag                  | Description |
| --------------------- | --- |
| abstract              | Cannot be instantiated with new(). |
| native                | Class is from the engine. |
| ui                    | Has UI scope. |
| play                  | Has Play scope. |
| replaces ReplaceClass | Replaces ReplaceClass with this class. Only works on objects which are descendants of Actor. |
| version("ver")        | Restricted to version <ver>. |

Example usages:

```cs
   class MyCoolObject play // automatically inherits Object
   class MyCoolThinker : Thinker // inherits Thinker
   class MyCoolActor : Actor replaces OtherActor
   class MyCoolInterface abstract // can only be inherited
```