There are some bugs in the rewrite, need some elbow-grease to iron them out

src/game.rs

@@ -484,8 +484,8 @@ impl Board {
     fn line(&self, from: BoardIndex, to: BoardIndex) -> impl Iterator<Item = BoardIndex> {
         let mut curr = from;
 
-        // Longest possible move is 10, so we create a generator over 11
-        (0..11)
+        // Longest possible move is 10, so we create a generator over 12
+        (0..12)
             .map(move |_| {
                 let x = if curr.x > to.x {
                     curr.x.saturating_sub(1)
@@ -534,7 +534,19 @@ impl Board {
                             // Cannot move on top of a friendly
                             Some(_) => Some(MoveType::Invalid),
                             // Any other spot is valid
-                            None => Some(MoveType::Valid),
+                            None => {
+                                // If there is another piece between A and B
+                                if self
+                                    .line(from, to)
+                                    .any(|board_index| self.at(board_index).is_some())
+                                {
+                                    // Invalid move, there is a piece between A and B
+                                    Some(MoveType::Invalid)
+                                } else {
+                                    // Otherwise it's a valid
+                                    Some(MoveType::Valid)
+                                }
+                            }
                         }
                     }
                     // Check for moving across the canal