docs: document root module

Cargo.toml

@@ -2,7 +2,7 @@
 name = "sparsey"
 version = "0.12.1"
 edition = "2021"
-description = "Sparse set-based entity component system"
+description = "Entity Component System based on sparse sets"
 authors = ["Tudor-Cristian Lechințan <[email protected]>"]
 repository = "https://github.com/LechintanTudor/sparsey"
 keywords = ["component", "ecs", "entity", "gamedev", "system"]
@@ -22,12 +22,9 @@ features = ["inline-more"]
 
 [features]
 default = ["std"]
-std = []
+std = ["rustc-hash/std"]
 parallel = ["std", "dep:rayon"]
 
-[lints.rust]
-# missing-docs = "forbid"
-
 [lints.clippy]
 pedantic = { level = "warn", priority = -1 }
 cast-possible-truncation = "allow"

src/lib.rs

@@ -1,4 +1,42 @@
-#![no_std]
+//! Sparsey is an [Entity Component System (ECS)](https://www.geeksforgeeks.org/sparse-set/)
+//! based on [sparse sets](https://www.geeksforgeeks.org/sparse-set/).
+//!
+//! # Example
+//! ```rust
+//! use sparsey::World;
+//!
+//! struct Position(i32, i32);
+//! struct Velocity(i32, i32);
+//!
+//! fn main() {
+//! let mut world = World::builder()
+//! .register::<Position>()
+//! .register::<Velocity>()
+//! .build();
+//!
+//! world.create((Position(0, 0), Velocity(1, 2)));
+//! world.create((Position(0, 0), Velocity(2, 3)));
+//! 
+//! world.for_each::<(&mut Position, &Velocity)>(|(position, velocity)| {
+//! position.0 += velocity.0;
+//! position.1 += velocity.1;
+//! });
+//! }
+//! ```
+//!
+//! # Features
+//!
+//! - `std` (on by default): link to the `std` crate.
+//! - `parallel`: enable parallel iterators.
+//!
+//! # Usage
+//!
+//! The most important items from Sparsey crate are [`World`] and [`Entity`], which are re-exported
+//! at the root of the crate for easy access. A [`World`] is a collection of entities and components
+//! thas supports create/read/update/delete (CRUD) operations, while an [`Entity`] is a versioned
+//! index used to reference components within a [`World`].
+
+#![cfg_attr(not(feature = "std"), no_std)]
 
 extern crate alloc;