### Declare Component Structs

Source: https://github.com/prime31/zig-ecs/blob/master/README.md

Defines example component structures, Velocity and Position, which will be used with the ECS.

```zig
pub const Velocity = struct { x: f32, y: f32 };
pub const Position = struct { x: f32, y: f32 };
```

--------------------------------

### Create Entities and Add Components

Source: https://github.com/prime31/zig-ecs/blob/master/README.md

Demonstrates creating entities and adding Position and Velocity components to them.

```zig
const entity = reg.create();
reg.add(entity, Position{ .x = 0, .y = 0 });
reg.add(entity, Velocity{ .x = 5, .y = 7 });
```

--------------------------------

### Initialize ECS Registry

Source: https://github.com/prime31/zig-ecs/blob/master/README.md

Initializes the ECS Registry, which manages entity data and query execution.

```zig
var reg = ecs.Registry.init(std.testing.allocator);
```

--------------------------------

### Iterate Entities with a View

Source: https://github.com/prime31/zig-ecs/blob/master/README.md

Shows how to create and iterate a View that matches entities with both Velocity and Position components, accessing components mutably and immutably.

```zig
var view = reg.view(.{ Velocity, Position }, .{});

var iter = view.entityIterator();
while (iter.next()) |entity| {
    const pos = view.getConst(Position, entity); // readonly copy
    var vel = view.get(Velocity, entity); // mutable
}
```

--------------------------------

### Iterate Entities with an Owning Group

Source: https://github.com/prime31/zig-ecs/blob/master/README.md

Demonstrates using an owning Group to iterate over entities and update their components using a callback function.

```zig
var group = reg.group(.{ Velocity, Position }, .{}, .{});
group.each(each);

fn each(e: struct { vel: *Velocity, pos: *Position }) void {
    e.pos.*.x += e.vel.x;
    e.pos.*.y += e.vel.y;
}
```

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