diff --git a/gomori/src/board.rs b/gomori/src/board.rs
index 1ef6955..e661b1e 100644
--- a/gomori/src/board.rs
+++ b/gomori/src/board.rs
@@ -44,7 +44,7 @@ struct Diff {
 
 /// The effects that playing a card would have.
 ///
-/// Returned by [`Board::execute()`].
+/// Returned by [`Board::calculate()`].
 pub struct CalculatedEffects<'a> {
     /// This struct ties together the board and its diff, to prevent any possible mixups
     board: &'a Board,
@@ -146,12 +146,7 @@ impl Board {
             let mut set = CardsSet::new();
             for &(i, j, field) in &self.fields {
                 if won.contains(i, j) {
-                    for card in field.hidden_cards() {
-                        set = set.insert(card);
-                    }
-                    if let Some(card) = field.top_card() {
-                        set = set.insert(card);
-                    }
+                    set |= field.all_cards();
                 }
             }
             set
@@ -260,6 +255,17 @@ impl Board {
         bitboard
     }
 
+    /// Returns all the coordinates that already have a card on them and are valid places to play the given card.
+    pub fn combo_locations_for_card(&self, card: Card) -> BitBoard {
+        let mut bitboard = BitBoard::empty_board_centered_at(self.fields[0].0, self.fields[0].1);
+        for &(i, j, field) in &self.fields {
+            if field.can_place_card(card) {
+                bitboard = bitboard.insert(i, j);
+            }
+        }
+        bitboard
+    }
+
     /// Returns a [`CompactField`] if there are any cards at the given coordinate.
     pub fn get(&self, i: i8, j: i8) -> Option<CompactField> {
         for &(i_field, j_field, compact_field) in &self.fields {
@@ -499,6 +505,11 @@ mod python {
             self.locations_for_card(card)
         }
 
+        #[pyo3(name = "combo_locations_for_card")]
+        fn py_combo_locations_for_card(&self, card: Card) -> BitBoard {
+            self.combo_locations_for_card(card)
+        }
+
         #[pyo3(name = "get")]
         fn py_get(&self, i: i8, j: i8) -> Option<CompactField> {
             self.get(i, j)
diff --git a/gomori/src/board/compact_field.rs b/gomori/src/board/compact_field.rs
index e46452e..991831e 100644
--- a/gomori/src/board/compact_field.rs
+++ b/gomori/src/board/compact_field.rs
@@ -87,7 +87,7 @@ impl CompactField {
 
     /// All cards on the field.
     ///
-    /// Equal to [`hidden_cards()`] + [`top_card()`], if any.
+    /// Equal to [`hidden_cards()`](Self::hidden_cards) + [`top_card()`](Self::top_card), if any.
     pub fn all_cards(self) -> CardsSet {
         if let Some(c) = self.top_card() {
             self.hidden_cards().insert(c)
diff --git a/gomori/src/cards_set.rs b/gomori/src/cards_set.rs
index f881738..3cb09ff 100644
--- a/gomori/src/cards_set.rs
+++ b/gomori/src/cards_set.rs
@@ -5,6 +5,16 @@ use crate::Card;
 /// Allows intersection/union/xor with other such sets via bitwise ops.
 /// Also implements [`IntoIterator`], so it can be converted into e.g.
 /// a vector with `Vec::from_iter(cards_set)`.
+///
+/// ```
+/// use gomori::{card, CardsSet};
+/// let mut set = CardsSet::new();
+/// // This is an immutable data type, so functions like `insert` return a new `CardsSet`.
+/// set = set.insert(card!("7♥"));
+/// set = set.insert(card!("7♥"));  // Inserting a second time has no effect
+/// set = set.insert(card!("2♥"));
+/// assert_eq!(Vec::from_iter(set), vec![card!("2♥"), card!("7♥")]);
+/// ```
 #[cfg_attr(feature = "python", pyo3::pyclass)]
 #[derive(Clone, Copy, Debug, PartialEq, Eq)]
 pub struct CardsSet {
diff --git a/gomori/src/errors.rs b/gomori/src/errors.rs
index 4fbc796..0cae75c 100644
--- a/gomori/src/errors.rs
+++ b/gomori/src/errors.rs
@@ -124,7 +124,7 @@ mod python {
         gomori,
         IllegalMoveException,
         pyo3::exceptions::PyException,
-        "Describes why the card cannot be played."
+        "Describes why a move is illegal."
     );
 
     impl From<IllegalMove> for PyErr {
diff --git a/gomori/src/protocol_types.rs b/gomori/src/protocol_types.rs
index 100d99d..a5b770a 100644
--- a/gomori/src/protocol_types.rs
+++ b/gomori/src/protocol_types.rs
@@ -45,6 +45,7 @@ pub enum Request {
 #[derive(Clone, Debug, Serialize, Deserialize)]
 pub struct Okay();
 
+/// Black or white.
 #[cfg_attr(feature = "python", pyo3::pyclass)]
 #[derive(Clone, Copy, Debug, PartialEq, Eq, Serialize, Deserialize)]
 #[serde(rename_all = "lowercase")]