diff --git a/src/board/castle_rights.rs b/src/board/castle_rights.rs
deleted file mode 100644
index 0e44e03..0000000
--- a/src/board/castle_rights.rs
+++ /dev/null
@@ -1,196 +0,0 @@
-use super::{Bitboard, Color, File, Square};
-
-/// Current castle rights for a player.
-#[derive(Copy, Clone, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
-pub enum CastleRights {
-    /// No castling allowed.
-    NoSide,
-    /// King-side castling only.
-    KingSide,
-    /// Queen-side castling only.
-    QueenSide,
-    /// Either side allowed.
-    BothSides,
-}
-
-impl CastleRights {
-    /// Convert from a castle rights index into a [CastleRights] type.
-    #[inline(always)]
-    pub fn from_index(index: usize) -> Self {
-        assert!(index < 4);
-        // SAFETY: we know the value is in-bounds
-        unsafe { Self::from_index_unchecked(index) }
-    }
-
-    /// Convert from a castle rights index into a [CastleRights] type, no bounds checking.
-    #[inline(always)]
-    pub unsafe fn from_index_unchecked(index: usize) -> Self {
-        std::mem::transmute(index as u8)
-    }
-
-    /// Return the index of a given [CastleRights].
-    #[inline(always)]
-    pub fn index(self) -> usize {
-        self as usize
-    }
-
-    /// Can the player castle king-side.
-    #[inline(always)]
-    pub fn has_king_side(self) -> bool {
-        (self.index() & 1) != 0
-    }
-
-    /// Can the player castle king-side.
-    #[inline(always)]
-    pub fn has_queen_side(self) -> bool {
-        (self.index() & 2) != 0
-    }
-
-    /// Remove king-side castling rights.
-    #[inline(always)]
-    pub fn without_king_side(self) -> Self {
-        self.remove(Self::KingSide)
-    }
-
-    /// Remove queen-side castling rights.
-    #[inline(always)]
-    pub fn without_queen_side(self) -> Self {
-        self.remove(Self::QueenSide)
-    }
-
-    /// Remove some [CastleRights], and return the resulting [CastleRights].
-    #[inline(always)]
-    pub fn remove(self, to_remove: CastleRights) -> Self {
-        // SAFETY: we know the value is in-bounds
-        unsafe { Self::from_index_unchecked(self.index() & !to_remove.index()) }
-    }
-
-    /// Which rooks have not been moved for a given [CastleRights] and [Color].
-    #[inline(always)]
-    pub fn unmoved_rooks(self, color: Color) -> Bitboard {
-        let rank = color.first_rank();
-
-        let king_side_square = Square::new(File::H, rank);
-        let queen_side_square = Square::new(File::A, rank);
-
-        match self {
-            Self::NoSide => Bitboard::EMPTY,
-            Self::KingSide => king_side_square.into_bitboard(),
-            Self::QueenSide => queen_side_square.into_bitboard(),
-            Self::BothSides => king_side_square | queen_side_square,
-        }
-    }
-}
-
-#[cfg(test)]
-mod test {
-    use super::*;
-
-    #[test]
-    fn from_index() {
-        assert_eq!(CastleRights::from_index(0), CastleRights::NoSide);
-        assert_eq!(CastleRights::from_index(1), CastleRights::KingSide);
-        assert_eq!(CastleRights::from_index(2), CastleRights::QueenSide);
-        assert_eq!(CastleRights::from_index(3), CastleRights::BothSides);
-    }
-
-    #[test]
-    fn index() {
-        assert_eq!(CastleRights::NoSide.index(), 0);
-        assert_eq!(CastleRights::KingSide.index(), 1);
-        assert_eq!(CastleRights::QueenSide.index(), 2);
-        assert_eq!(CastleRights::BothSides.index(), 3);
-    }
-
-    #[test]
-    fn has_kingside() {
-        assert!(!CastleRights::NoSide.has_king_side());
-        assert!(!CastleRights::QueenSide.has_king_side());
-        assert!(CastleRights::KingSide.has_king_side());
-        assert!(CastleRights::BothSides.has_king_side());
-    }
-
-    #[test]
-    fn has_queenside() {
-        assert!(!CastleRights::NoSide.has_queen_side());
-        assert!(!CastleRights::KingSide.has_queen_side());
-        assert!(CastleRights::QueenSide.has_queen_side());
-        assert!(CastleRights::BothSides.has_queen_side());
-    }
-
-    #[test]
-    fn without_king_side() {
-        assert_eq!(
-            CastleRights::NoSide.without_king_side(),
-            CastleRights::NoSide
-        );
-        assert_eq!(
-            CastleRights::KingSide.without_king_side(),
-            CastleRights::NoSide
-        );
-        assert_eq!(
-            CastleRights::QueenSide.without_king_side(),
-            CastleRights::QueenSide
-        );
-        assert_eq!(
-            CastleRights::BothSides.without_king_side(),
-            CastleRights::QueenSide
-        );
-    }
-
-    #[test]
-    fn without_queen_side() {
-        assert_eq!(
-            CastleRights::NoSide.without_queen_side(),
-            CastleRights::NoSide
-        );
-        assert_eq!(
-            CastleRights::QueenSide.without_queen_side(),
-            CastleRights::NoSide
-        );
-        assert_eq!(
-            CastleRights::KingSide.without_queen_side(),
-            CastleRights::KingSide
-        );
-        assert_eq!(
-            CastleRights::BothSides.without_queen_side(),
-            CastleRights::KingSide
-        );
-    }
-
-    #[test]
-    fn unmoved_rooks() {
-        assert_eq!(
-            CastleRights::NoSide.unmoved_rooks(Color::White),
-            Bitboard::EMPTY
-        );
-        assert_eq!(
-            CastleRights::NoSide.unmoved_rooks(Color::Black),
-            Bitboard::EMPTY
-        );
-        assert_eq!(
-            CastleRights::KingSide.unmoved_rooks(Color::White),
-            Square::H1.into_bitboard()
-        );
-        assert_eq!(
-            CastleRights::KingSide.unmoved_rooks(Color::Black),
-            Square::H8.into_bitboard()
-        );
-        assert_eq!(
-            CastleRights::QueenSide.unmoved_rooks(Color::White),
-            Square::A1.into_bitboard()
-        );
-        assert_eq!(
-            CastleRights::QueenSide.unmoved_rooks(Color::Black),
-            Square::A8.into_bitboard()
-        );
-        assert_eq!(
-            CastleRights::BothSides.unmoved_rooks(Color::White),
-            Square::A1 | Square::H1
-        );
-        assert_eq!(
-            CastleRights::BothSides.unmoved_rooks(Color::Black),
-            Square::A8 | Square::H8
-        );
-    }
-}
diff --git a/src/board/color.rs b/src/board/color.rs
deleted file mode 100644
index a7af8b6..0000000
--- a/src/board/color.rs
+++ /dev/null
@@ -1,102 +0,0 @@
-use super::Rank;
-
-/// An enum representing the color of a player.
-#[derive(Copy, Clone, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
-pub enum Color {
-    White,
-    Black,
-}
-
-impl Color {
-    /// Convert from a file index into a [Color] type.
-    #[inline(always)]
-    pub fn from_index(index: usize) -> Self {
-        assert!(index < 2);
-        // SAFETY: we know the value is in-bounds
-        unsafe { Self::from_index_unchecked(index) }
-    }
-
-    /// Convert from a file index into a [Color] type, no bounds checking.
-    #[inline(always)]
-    pub unsafe fn from_index_unchecked(index: usize) -> Self {
-        std::mem::transmute(index as u8)
-    }
-
-    /// Return the index of a given [Color].
-    #[inline(always)]
-    pub fn index(self) -> usize {
-        self as usize
-    }
-
-    /// Return the first [Rank] for pieces of the given [Color], where its pieces start.
-    #[inline(always)]
-    pub fn first_rank(self) -> Rank {
-        match self {
-            Self::White => Rank::First,
-            Self::Black => Rank::Eighth,
-        }
-    }
-
-    /// Return the second [Rank] for pieces of the given [Color], where its pawns start.
-    #[inline(always)]
-    pub fn second_rank(self) -> Rank {
-        match self {
-            Self::White => Rank::Second,
-            Self::Black => Rank::Seventh,
-        }
-    }
-
-    /// Return the fourth [Rank] for pieces of the given [Color], where its pawns move to after a
-    /// two-square move.
-    #[inline(always)]
-    pub fn fourth_rank(self) -> Rank {
-        match self {
-            Self::White => Rank::Fourth,
-            Self::Black => Rank::Fifth,
-        }
-    }
-
-    /// Return the seventh [Rank] for pieces of the given [Color], which is the rank before a pawn
-    /// gets promoted.
-    #[inline(always)]
-    pub fn seventh_rank(self) -> Rank {
-        match self {
-            Self::White => Rank::Seventh,
-            Self::Black => Rank::Second,
-        }
-    }
-}
-
-impl std::ops::Not for Color {
-    type Output = Color;
-
-    fn not(self) -> Self::Output {
-        match self {
-            Self::White => Self::Black,
-            Self::Black => Self::White,
-        }
-    }
-}
-
-#[cfg(test)]
-mod test {
-    use super::*;
-
-    #[test]
-    fn from_index() {
-        assert_eq!(Color::from_index(0), Color::White);
-        assert_eq!(Color::from_index(1), Color::Black);
-    }
-
-    #[test]
-    fn index() {
-        assert_eq!(Color::White.index(), 0);
-        assert_eq!(Color::Black.index(), 1);
-    }
-
-    #[test]
-    fn not() {
-        assert_eq!(!Color::White, Color::Black);
-        assert_eq!(!Color::Black, Color::White);
-    }
-}
diff --git a/src/board/direction.rs b/src/board/directions.rs
similarity index 100%
rename from src/board/direction.rs
rename to src/board/directions.rs
diff --git a/src/board/mod.rs b/src/board/mod.rs
index ad91192..bc9d1d9 100644
--- a/src/board/mod.rs
+++ b/src/board/mod.rs
@@ -1,14 +1,8 @@
 pub mod bitboard;
 pub use bitboard::*;
 
-pub mod castle_rights;
-pub use castle_rights::*;
-
-pub mod color;
-pub use color::*;
-
-pub mod direction;
-pub use direction::*;
+pub mod directions;
+pub use directions::*;
 
 pub mod file;
 pub use file::*;