diff --git a/board-shared/src/ai.rs b/board-shared/src/ai.rs
index f5e968a..8fc779d 100644
--- a/board-shared/src/ai.rs
+++ b/board-shared/src/ai.rs
@@ -74,7 +74,7 @@ pub fn generate_valid_combinations(
     // Separate numbers and operators
     let mut numbers = Vec::new();
     let mut operators = Vec::new();
-    for &tile in &hand.tiles {
+    for &tile in &context.tiles().tiles {
         match tile {
             Tile::Digit(digit) => numbers.push(digit),
             Tile::Operator(operator) => operators.push(operator),
@@ -193,21 +193,19 @@ mod tests {
             Tile::Digit(Digit::new(-6)),
             Tile::Operator(Operator::Add),
         ]);
-        let board = Board::new(3, 3);
-        board.set_tile(1, 0, Tile::Digit(Digit::new(9)));
-        board.set_tile(1, 1, Tile::Equals);
-        board.set_tile(1, 2, Tile::Digit(Digit::new(9)));
+        let mut board = Board::new(3, 3);
+        board.set(1, 0, Tile::Digit(Digit::new(9)));
+        board.set(1, 1, Tile::Equals);
+        board.set(1, 2, Tile::Digit(Digit::new(9)));
         let combinations = generate_valid_combinations(
             CombinationConfig::default(),
             BoardGenerationContext::new(&hand, &board),
         );
-        assert_eq!(
-            combinations,
-            vec![vec![
-                Tile::Digit(Digit::new(-5)),
-                Tile::Equals,
-                Tile::Digit(Digit::new(-5)),
-            ]]
-        );
+        let tiles = vec![
+            Tile::Digit(Digit::new(-5)),
+            Tile::Equals,
+            Tile::Digit(Digit::new(-5)),
+        ];
+        assert_eq!(combinations, vec![tiles.clone(), tiles]);
     }
 }
diff --git a/board-shared/src/board.rs b/board-shared/src/board.rs
index 53cfdff..f2d980a 100644
--- a/board-shared/src/board.rs
+++ b/board-shared/src/board.rs
@@ -131,7 +131,8 @@ impl Board {
         direction: Direction,
     ) -> bool {
         let mut pos = starting_from;
-        for tile in tiles {
+        let mut it = tiles.iter();
+        while let Some(tile) = it.next() {
             if let Some(existing) = self.get(pos.x, pos.y) {
                 if existing != *tile {
                     return false;
@@ -140,7 +141,7 @@ impl Board {
             if let Some(relative) = pos.relative(direction, self) {
                 pos = relative;
             } else {
-                return false;
+                return it.next().is_none();
             }
         }
         true
@@ -418,4 +419,59 @@ mod tests {
         assert_eq!(board.is_unique_chain(&positions(&[(1, 1), (2, 1)])), true);
         assert_eq!(board.is_unique_chain(&positions(&[(1, 1), (3, 1)])), false);
     }
+
+    #[test]
+    fn test_is_playable() {
+        let board = Board::new(5, 5);
+        let tiles = vec![
+            Tile::Digit(Digit::new(5)),
+            Tile::Digit(Digit::new(6)),
+            Tile::Digit(Digit::new(9)),
+        ];
+        assert_eq!(
+            board.is_playable(&tiles, (1, 1).into(), Direction::Right),
+            true
+        );
+        assert_eq!(
+            board.is_playable(&tiles, (4, 0).into(), Direction::Down),
+            true
+        );
+    }
+
+    #[test]
+    fn test_is_playable_constrained() {
+        let board = Board::new(2, 2);
+        let tiles = vec![Tile::Digit(Digit::new(7)), Tile::Digit(Digit::new(8))];
+        assert_eq!(
+            board.is_playable(&tiles, (0, 0).into(), Direction::Right),
+            true
+        );
+        assert_eq!(
+            board.is_playable(&tiles, (0, 0).into(), Direction::Down),
+            true
+        );
+        assert_eq!(
+            board.is_playable(&tiles, (1, 0).into(), Direction::Right),
+            false
+        );
+    }
+
+    #[test]
+    fn test_is_playable_blocking_pieces() {
+        let mut board = Board::new(3, 3);
+        board.set(1, 1, Tile::Digit(Digit::new(1)));
+        let tiles = vec![Tile::Digit(Digit::new(0)), Tile::Digit(Digit::new(0))];
+        assert_eq!(
+            board.is_playable(&tiles, (0, 0).into(), Direction::Right),
+            true
+        );
+        assert_eq!(
+            board.is_playable(&tiles, (0, 1).into(), Direction::Right),
+            false
+        );
+        assert_eq!(
+            board.is_playable(&tiles, (1, 0).into(), Direction::Down),
+            false
+        );
+    }
 }
diff --git a/board-shared/src/position.rs b/board-shared/src/position.rs
index 8836f41..8aa53ea 100644
--- a/board-shared/src/position.rs
+++ b/board-shared/src/position.rs
@@ -154,7 +154,11 @@ impl Iterator for RowByRowIterator {
         } else {
             let pos = self.pos;
             self.pos = if self.pos.x == self.end.x - 1 {
-                Position2d::new(0, self.pos.y + 1)
+                if self.pos.y == self.end.y - 1 {
+                    self.end
+                } else {
+                    Position2d::new(0, self.pos.y + 1)
+                }
             } else {
                 Position2d::new(self.pos.x + 1, self.pos.y)
             };
@@ -215,4 +219,24 @@ mod tests {
         );
         assert_eq!(pos.relative(Direction::Right, &rect), None);
     }
+
+    #[test]
+    fn test_empty_row_iter() {
+        let rect = Rectangle::new(0, 0);
+        let mut iter = rect.row_iter();
+        assert_eq!(iter.next(), None);
+    }
+
+    #[test]
+    fn test_row_iter() {
+        let rect = Rectangle::new(3, 2);
+        let mut iter = rect.row_iter();
+        assert_eq!(iter.next(), Some(Position2d::new(0, 0)));
+        assert_eq!(iter.next(), Some(Position2d::new(1, 0)));
+        assert_eq!(iter.next(), Some(Position2d::new(2, 0)));
+        assert_eq!(iter.next(), Some(Position2d::new(0, 1)));
+        assert_eq!(iter.next(), Some(Position2d::new(1, 1)));
+        assert_eq!(iter.next(), Some(Position2d::new(2, 1)));
+        assert_eq!(iter.next(), None);
+    }
 }