diff --git a/src/chunk.rs b/src/chunk.rs
index fa1d939..731b827 100644
--- a/src/chunk.rs
+++ b/src/chunk.rs
@@ -76,6 +76,11 @@ impl<C: Config> Chunks<C> {
         self.chunks.len()
     }
 
+    /// Returns `true` if there are no loaded chunks.
+    pub fn is_empty(&self) -> bool {
+        self.chunks.len() == 0
+    }
+
     /// Gets a shared reference to the chunk at the provided position.
     ///
     /// If there is no chunk at the position, then `None` is returned.
diff --git a/src/client.rs b/src/client.rs
index af60405..16636a3 100644
--- a/src/client.rs
+++ b/src/client.rs
@@ -90,6 +90,12 @@ impl<C: Config> Clients<C> {
         self.slab.len()
     }
 
+    /// Returns `true` if there are no clients on the server. This includes
+    /// clients for which [`Client::is_disconnected`] returns true.
+    pub fn is_empty(&self) -> bool {
+        self.slab.len() == 0
+    }
+
     /// Returns a shared reference to the client with the given ID. If
     /// the ID is invalid, then `None` is returned.
     pub fn get(&self, client: ClientId) -> Option<&Client<C>> {
diff --git a/src/entity.rs b/src/entity.rs
index b2c374b..23bbe06 100644
--- a/src/entity.rs
+++ b/src/entity.rs
@@ -146,6 +146,11 @@ impl<C: Config> Entities<C> {
         self.slab.len()
     }
 
+    /// Returns `true` if there are no entities.
+    pub fn is_empty(&self) -> bool {
+        self.slab.len() == 0
+    }
+
     /// Gets the [`EntityId`] of the entity with the given UUID in an efficient
     /// manner.
     ///
diff --git a/src/player_list.rs b/src/player_list.rs
index f51f2bd..9abfe30 100644
--- a/src/player_list.rs
+++ b/src/player_list.rs
@@ -40,7 +40,11 @@ impl<C: Config> PlayerLists<C> {
         }
     }
 
+    /// Creates a new player list and returns an exclusive reference to it along
+    /// with its ID.
     ///
+    /// The player list is automatically removed at the end of the tick once all
+    /// IDs to it have been dropped.
     pub fn insert(&mut self, state: C::PlayerListState) -> (PlayerListId, &mut PlayerList<C>) {
         let (key, pl) = self.slab.insert(PlayerList {
             state,
@@ -54,14 +58,28 @@ impl<C: Config> PlayerLists<C> {
         (PlayerListId(key), pl)
     }
 
+    /// Returns the number of player lists.
     pub fn len(&self) -> usize {
         self.slab.len()
     }
 
+    /// Returns `true` if there are no player lists.
+    pub fn is_empty(&self) -> bool {
+        self.slab.len() == 0
+    }
+
+    /// Gets a shared reference to the player list with the given player list
+    /// ID.
+    ///
+    /// This operation is infallible because [`PlayerListId`] is refcounted.
     pub fn get(&self, id: &PlayerListId) -> &PlayerList<C> {
         self.slab.get(&id.0)
     }
 
+    /// Gets an exclusive reference to the player list with the given player
+    /// list ID.
+    ///
+    /// This operation is infallible because [`PlayerListId`] is refcounted.
     pub fn get_mut(&mut self, id: &PlayerListId) -> &mut PlayerList<C> {
         self.slab.get_mut(&id.0)
     }
diff --git a/src/slab.rs b/src/slab.rs
index 1471956..b95e637 100644
--- a/src/slab.rs
+++ b/src/slab.rs
@@ -297,7 +297,7 @@ impl<T> FusedIterator for IterMut<'_, T> {}
 
 impl<T> Clone for ParIter<'_, T> {
     fn clone(&self) -> Self {
-        Self { slab: &self.slab }
+        Self { slab: self.slab }
     }
 }
 
diff --git a/src/slab_rc.rs b/src/slab_rc.rs
index b996569..40da6ce 100644
--- a/src/slab_rc.rs
+++ b/src/slab_rc.rs
@@ -29,7 +29,7 @@ impl<T: Clone> Clone for Slot<T> {
     }
 }
 
-#[derive(Clone, Eq, Ord, Debug)]
+#[derive(Clone, Eq, Debug)]
 pub struct Key(Arc<usize>);
 
 impl PartialEq for Key {
@@ -44,6 +44,12 @@ impl PartialOrd for Key {
     }
 }
 
+impl Ord for Key {
+    fn cmp(&self, other: &Self) -> Ordering {
+        self.partial_cmp(other).unwrap()
+    }
+}
+
 impl Hash for Key {
     fn hash<H: Hasher>(&self, state: &mut H) {
         Arc::as_ptr(&self.0).hash(state)
diff --git a/src/slab_versioned.rs b/src/slab_versioned.rs
index e4ecced..86c039b 100644
--- a/src/slab_versioned.rs
+++ b/src/slab_versioned.rs
@@ -68,12 +68,12 @@ impl<T> VersionedSlab<T> {
 
     pub fn get(&self, key: Key) -> Option<&T> {
         let slot = self.slab.get(key.index as usize)?;
-        (slot.version == key.version).then(|| &slot.value)
+        (slot.version == key.version).then_some(&slot.value)
     }
 
     pub fn get_mut(&mut self, key: Key) -> Option<&mut T> {
         let slot = self.slab.get_mut(key.index as usize)?;
-        (slot.version == key.version).then(|| &mut slot.value)
+        (slot.version == key.version).then_some(&mut slot.value)
     }
 
     pub fn len(&self) -> usize {
diff --git a/src/world.rs b/src/world.rs
index 03ec5e3..2c8e7ca 100644
--- a/src/world.rs
+++ b/src/world.rs
@@ -79,6 +79,11 @@ impl<C: Config> Worlds<C> {
         self.slab.len()
     }
 
+    /// Returns `true` if there are no worlds on the server.
+    pub fn is_empty(&self) -> bool {
+        self.slab.len() == 0
+    }
+
     /// Returns a shared reference to the world with the given ID. If
     /// the ID is invalid, then `None` is returned.
     pub fn get(&self, world: WorldId) -> Option<&World<C>> {