diff --git a/src/bitboard.rs b/src/bitboard.rs
index b2d728b..a36fd0e 100644
--- a/src/bitboard.rs
+++ b/src/bitboard.rs
@@ -1,19 +1,22 @@
+//! Sets of squares.
+
 use crate::board::*;
 
 use std::iter::ExactSizeIterator;
 use std::iter::FusedIterator;
 
+/// A set of squares.
 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
-pub struct Bitboard(pub(crate) u64);
+pub struct Bitboard(pub u64);
 
 impl Bitboard {
     #[inline]
-    pub fn new() -> Self {
+    pub const fn new() -> Self {
         Self(0)
     }
 
     #[inline]
-    pub fn is_empty(&self) -> bool {
+    pub const fn is_empty(&self) -> bool {
         self.0 == 0
     }
 
@@ -38,7 +41,7 @@ impl Bitboard {
     }
 
     #[inline]
-    pub fn pop(&mut self) -> Option<Square> {
+    pub const fn pop(&mut self) -> Option<Square> {
         let Self(ref mut mask) = self;
         let square = match mask {
             0 => None,
@@ -54,7 +57,23 @@ impl Bitboard {
     }
 
     #[inline]
-    pub fn trans(&self, direction: Direction) -> Self {
+    pub const fn contains(&self, square: Square) -> bool {
+        self.0 & (1 << square as u8) != 0
+    }
+
+    #[inline]
+    pub const fn remove(&mut self, _square: Square) {
+        todo!()
+    }
+
+    #[inline]
+    pub fn mirror(self) -> Bitboard {
+        let [a, b, c, d, e, f, g, h] = self.0.to_le_bytes();
+        Self(u64::from_le_bytes([h, g, f, e, d, c, b, a]))
+    }
+
+    #[inline]
+    pub(crate) fn trans(&self, direction: Direction) -> Self {
         match direction {
             Direction::North => Self(self.0 << 8),
             Direction::NorthEast => Self(self.0 << 9) & !File::A.bitboard(),
@@ -66,17 +85,6 @@ impl Bitboard {
             Direction::NorthWest => Self(self.0 << 7) & !File::H.bitboard(),
         }
     }
-
-    #[inline]
-    pub const fn contains(&self, square: Square) -> bool {
-        self.0 & (1 << square as u8) != 0
-    }
-
-    #[inline]
-    pub fn mirror(self) -> Bitboard {
-        let [a, b, c, d, e, f, g, h] = self.0.to_le_bytes();
-        Self(u64::from_le_bytes([h, g, f, e, d, c, b, a]))
-    }
 }
 
 impl std::ops::BitOr for Bitboard {
diff --git a/src/board.rs b/src/board.rs
index 2cc880e..2911c56 100644
--- a/src/board.rs
+++ b/src/board.rs
@@ -155,7 +155,7 @@ impl File {
     }
 
     #[inline]
-    pub(crate) const fn bitboard(self) -> Bitboard {
+    pub const fn bitboard(self) -> Bitboard {
         Bitboard(0x0101010101010101 << (self as u8))
     }
 }
@@ -242,7 +242,7 @@ impl Rank {
     }
 
     #[inline]
-    pub(crate) const fn bitboard(self) -> Bitboard {
+    pub const fn bitboard(self) -> Bitboard {
         Bitboard(0xFF << ((self as u64) << 3))
     }
 }
@@ -326,7 +326,7 @@ impl Square {
     }
 
     #[inline]
-    pub(crate) const fn bitboard(self) -> Bitboard {
+    pub const fn bitboard(self) -> Bitboard {
         Bitboard(1 << self as u8)
     }
 
diff --git a/src/lib.rs b/src/lib.rs
index 6b5e3c5..7df0d27 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -73,10 +73,10 @@
 //! - etc.
 
 pub(crate) mod array_vec;
-pub(crate) mod bitboard;
 pub(crate) mod lookup;
 pub(crate) mod magics;
 
+pub mod bitboard;
 pub mod board;
 pub mod position;
 pub mod san;