diff --git a/cspuz_solver_backend/src/board.rs b/cspuz_solver_backend/src/board.rs
index 88ecd132..43f87a01 100644
--- a/cspuz_solver_backend/src/board.rs
+++ b/cspuz_solver_backend/src/board.rs
@@ -421,6 +421,86 @@ impl Board {
         }
     }
 
+    /// Renders grid edges (for puzzles like Slitherlink, Litherslink, Crosswall).
+    ///
+    /// This helper function adds edge items to the board based on a GridEdges structure.
+    /// - Vertical edges are rendered at positions (y * 2 + 1, x * 2)
+    /// - Horizontal edges are rendered at positions (y * 2, x * 2 + 1)
+    ///
+    /// # Arguments
+    /// * `edges` - The grid edges to render (with .vertical and .horizontal fields)
+    /// * `color` - Color to use for the rendered edges
+    /// * `true_kind` - ItemKind to use when edge value is true
+    /// * `false_kind` - ItemKind to use when edge value is false
+    pub fn add_grid_edges(
+        &mut self,
+        edges: &graph::GridEdges<Vec<Vec<Option<bool>>>>,
+        color: &'static str,
+        true_kind: ItemKind,
+        false_kind: ItemKind,
+    ) {
+        let height = self.height;
+        let width = self.width;
+
+        // Render vertical edges
+        for y in 0..height {
+            for x in 0..=width {
+                if let Some(b) = edges.vertical[y][x] {
+                    self.push(Item {
+                        y: y * 2 + 1,
+                        x: x * 2,
+                        color,
+                        kind: if b { true_kind.clone() } else { false_kind.clone() },
+                    });
+                }
+            }
+        }
+
+        // Render horizontal edges
+        for y in 0..=height {
+            for x in 0..width {
+                if let Some(b) = edges.horizontal[y][x] {
+                    self.push(Item {
+                        y: y * 2,
+                        x: x * 2 + 1,
+                        color,
+                        kind: if b { true_kind.clone() } else { false_kind.clone() },
+                    });
+                }
+            }
+        }
+    }
+
+    /// Renders Block/Dot items based on boolean answer grid (for region-based puzzles).
+    ///
+    /// This helper function adds Block or Dot items to the board for cells that have
+    /// determined values in the answer grid.
+    ///
+    /// # Arguments
+    /// * `is_black` - Answer grid with Option<bool> values
+    /// * `color` - Color to use for the rendered items
+    pub fn add_block_dot_answer(
+        &mut self,
+        is_black: &Vec<Vec<Option<bool>>>,
+        color: &'static str,
+    ) {
+        let height = self.height;
+        let width = self.width;
+
+        for y in 0..height {
+            for x in 0..width {
+                if let Some(b) = is_black[y][x] {
+                    self.push(Item::cell(
+                        y,
+                        x,
+                        color,
+                        if b { ItemKind::Block } else { ItemKind::Dot },
+                    ));
+                }
+            }
+        }
+    }
+
     pub fn to_json(&self) -> String {
         let kind = "grid";
         let height = self.height;
diff --git a/cspuz_solver_backend/src/puzzle/akichiwake.rs b/cspuz_solver_backend/src/puzzle/akichiwake.rs
index c99a9ed5..4fab903a 100644
--- a/cspuz_solver_backend/src/puzzle/akichiwake.rs
+++ b/cspuz_solver_backend/src/puzzle/akichiwake.rs
@@ -25,19 +25,8 @@ pub fn solve(url: &str) -> Result<Board, &'static str> {
 
     board.add_borders(&borders, "black");
 
-    for y in 0..height {
-        for x in 0..width {
-            if let Some(is_black) = &is_black {
-                if let Some(b) = is_black[y][x] {
-                    board.push(Item::cell(
-                        y,
-                        x,
-                        "green",
-                        if b { ItemKind::Block } else { ItemKind::Dot },
-                    ));
-                }
-            }
-        }
+    if let Some(is_black) = &is_black {
+        board.add_block_dot_answer(is_black, "green");
     }
     let rooms = graph::borders_to_rooms(&borders);
     assert_eq!(rooms.len(), clues.len());
diff --git a/cspuz_solver_backend/src/puzzle/aqre.rs b/cspuz_solver_backend/src/puzzle/aqre.rs
index 8423d089..eee48806 100644
--- a/cspuz_solver_backend/src/puzzle/aqre.rs
+++ b/cspuz_solver_backend/src/puzzle/aqre.rs
@@ -25,19 +25,8 @@ pub fn solve(url: &str) -> Result<Board, &'static str> {
 
     board.add_borders(&borders, "black");
 
-    for y in 0..height {
-        for x in 0..width {
-            if let Some(is_black) = &is_black {
-                if let Some(b) = is_black[y][x] {
-                    board.push(Item::cell(
-                        y,
-                        x,
-                        "green",
-                        if b { ItemKind::Block } else { ItemKind::Dot },
-                    ));
-                }
-            }
-        }
+    if let Some(is_black) = &is_black {
+        board.add_block_dot_answer(is_black, "green");
     }
     let rooms = graph::borders_to_rooms(&borders);
     assert_eq!(rooms.len(), clues.len());
diff --git a/cspuz_solver_backend/src/puzzle/chocona.rs b/cspuz_solver_backend/src/puzzle/chocona.rs
index 448895cc..d42f0162 100644
--- a/cspuz_solver_backend/src/puzzle/chocona.rs
+++ b/cspuz_solver_backend/src/puzzle/chocona.rs
@@ -25,18 +25,7 @@ pub fn solve(url: &str) -> Result<Board, &'static str> {
     board.add_borders(&borders, "black");
 
     if let Some(is_black) = &is_black {
-        for y in 0..height {
-            for x in 0..width {
-                if let Some(b) = is_black[y][x] {
-                    board.push(Item::cell(
-                        y,
-                        x,
-                        "green",
-                        if b { ItemKind::Block } else { ItemKind::Dot },
-                    ));
-                }
-            }
-        }
+        board.add_block_dot_answer(is_black, "green");
     }
     let rooms = graph::borders_to_rooms(&borders);
     assert_eq!(rooms.len(), clues.len());
diff --git a/cspuz_solver_backend/src/puzzle/cocktail.rs b/cspuz_solver_backend/src/puzzle/cocktail.rs
index d1feb380..7fc82830 100644
--- a/cspuz_solver_backend/src/puzzle/cocktail.rs
+++ b/cspuz_solver_backend/src/puzzle/cocktail.rs
@@ -21,19 +21,8 @@ pub fn solve(url: &str) -> Result<Board, &'static str> {
 
     board.add_borders(&borders, "black");
 
-    if let Some(is_black) = is_black {
-        for y in 0..height {
-            for x in 0..width {
-                if let Some(b) = is_black[y][x] {
-                    board.push(Item::cell(
-                        y,
-                        x,
-                        "green",
-                        if b { ItemKind::Block } else { ItemKind::Dot },
-                    ));
-                }
-            }
-        }
+    if let Some(is_black) = &is_black {
+        board.add_block_dot_answer(is_black, "green");
     }
 
     let rooms = graph::borders_to_rooms(&borders);
diff --git a/cspuz_solver_backend/src/puzzle/crosswall.rs b/cspuz_solver_backend/src/puzzle/crosswall.rs
index a194f044..a4e60e97 100644
--- a/cspuz_solver_backend/src/puzzle/crosswall.rs
+++ b/cspuz_solver_backend/src/puzzle/crosswall.rs
@@ -28,31 +28,8 @@ pub fn solve(url: &str) -> Result<Board, &'static str> {
         }
     }
 
-    if let Some(is_line) = ans {
-        for y in 0..height {
-            for x in 0..=width {
-                if let Some(b) = is_line.vertical[y][x] {
-                    board.push(Item {
-                        y: y * 2 + 1,
-                        x: x * 2,
-                        color: "green",
-                        kind: if b { ItemKind::Wall } else { ItemKind::Cross },
-                    })
-                }
-            }
-        }
-        for y in 0..=height {
-            for x in 0..width {
-                if let Some(b) = is_line.horizontal[y][x] {
-                    board.push(Item {
-                        y: y * 2,
-                        x: x * 2 + 1,
-                        color: "green",
-                        kind: if b { ItemKind::Wall } else { ItemKind::Cross },
-                    })
-                }
-            }
-        }
+    if let Some(is_line) = &ans {
+        board.add_grid_edges(is_line, "green", ItemKind::Wall, ItemKind::Cross);
     }
 
     Ok(board)
diff --git a/cspuz_solver_backend/src/puzzle/double_lits.rs b/cspuz_solver_backend/src/puzzle/double_lits.rs
index c500f327..4800da6e 100644
--- a/cspuz_solver_backend/src/puzzle/double_lits.rs
+++ b/cspuz_solver_backend/src/puzzle/double_lits.rs
@@ -21,19 +21,8 @@ pub fn solve(url: &str) -> Result<Board, &'static str> {
 
     board.add_borders(&borders, "black");
 
-    if let Some(is_black) = ans {
-        for y in 0..height {
-            for x in 0..width {
-                if let Some(b) = is_black[y][x] {
-                    board.push(Item::cell(
-                        y,
-                        x,
-                        "green",
-                        if b { ItemKind::Block } else { ItemKind::Dot },
-                    ));
-                }
-            }
-        }
+    if let Some(is_black) = &ans {
+        board.add_block_dot_answer(is_black, "green");
     }
 
     Ok(board)
diff --git a/cspuz_solver_backend/src/puzzle/heyawake_internal.rs b/cspuz_solver_backend/src/puzzle/heyawake_internal.rs
index caadeb25..a695b6d6 100644
--- a/cspuz_solver_backend/src/puzzle/heyawake_internal.rs
+++ b/cspuz_solver_backend/src/puzzle/heyawake_internal.rs
@@ -41,19 +41,8 @@ pub fn solve(url: &str, is_ayeheya: bool) -> Result<Board, &'static str> {
 
     board.add_borders(&borders, "black");
 
-    for y in 0..height {
-        for x in 0..width {
-            if let Some(is_black) = &is_black {
-                if let Some(b) = is_black[y][x] {
-                    board.push(Item::cell(
-                        y,
-                        x,
-                        "green",
-                        if b { ItemKind::Block } else { ItemKind::Dot },
-                    ));
-                }
-            }
-        }
+    if let Some(is_black) = &is_black {
+        board.add_block_dot_answer(is_black, "green");
     }
     let rooms = graph::borders_to_rooms(&borders);
     assert_eq!(rooms.len(), clues.len());
diff --git a/cspuz_solver_backend/src/puzzle/inverse_litso.rs b/cspuz_solver_backend/src/puzzle/inverse_litso.rs
index 94d15837..121f961e 100644
--- a/cspuz_solver_backend/src/puzzle/inverse_litso.rs
+++ b/cspuz_solver_backend/src/puzzle/inverse_litso.rs
@@ -24,18 +24,7 @@ pub fn solve(url: &str) -> Result<Board, &'static str> {
     board.add_borders(&borders, "black");
 
     if let Some(is_black) = &is_black {
-        for y in 0..height {
-            for x in 0..width {
-                if let Some(b) = is_black[y][x] {
-                    board.push(Item::cell(
-                        y,
-                        x,
-                        "green",
-                        if b { ItemKind::Block } else { ItemKind::Dot },
-                    ));
-                }
-            }
-        }
+        board.add_block_dot_answer(is_black, "green");
     }
 
     Ok(board)
diff --git a/cspuz_solver_backend/src/puzzle/litherslink.rs b/cspuz_solver_backend/src/puzzle/litherslink.rs
index 808d8c5f..24ea4bba 100644
--- a/cspuz_solver_backend/src/puzzle/litherslink.rs
+++ b/cspuz_solver_backend/src/puzzle/litherslink.rs
@@ -23,30 +23,7 @@ pub fn solve(url: &str) -> Result<Board, &'static str> {
         }
     }
     if let Some(is_line) = &ans {
-        for y in 0..height {
-            for x in 0..=width {
-                if let Some(b) = is_line.vertical[y][x] {
-                    board.push(Item {
-                        y: y * 2 + 1,
-                        x: x * 2,
-                        color: "green",
-                        kind: if b { ItemKind::Wall } else { ItemKind::Cross },
-                    })
-                }
-            }
-        }
-        for y in 0..=height {
-            for x in 0..width {
-                if let Some(b) = is_line.horizontal[y][x] {
-                    board.push(Item {
-                        y: y * 2,
-                        x: x * 2 + 1,
-                        color: "green",
-                        kind: if b { ItemKind::Wall } else { ItemKind::Cross },
-                    })
-                }
-            }
-        }
+        board.add_grid_edges(is_line, "green", ItemKind::Wall, ItemKind::Cross);
     }
 
     Ok(board)
diff --git a/cspuz_solver_backend/src/puzzle/lits.rs b/cspuz_solver_backend/src/puzzle/lits.rs
index 5f1405e2..15d7266e 100644
--- a/cspuz_solver_backend/src/puzzle/lits.rs
+++ b/cspuz_solver_backend/src/puzzle/lits.rs
@@ -22,18 +22,7 @@ pub fn solve(url: &str) -> Result<Board, &'static str> {
     board.add_borders(&borders, "black");
 
     if let Some(is_black) = &ans {
-        for y in 0..height {
-            for x in 0..width {
-                if let Some(b) = is_black[y][x] {
-                    board.push(Item::cell(
-                        y,
-                        x,
-                        "green",
-                        if b { ItemKind::Block } else { ItemKind::Dot },
-                    ));
-                }
-            }
-        }
+        board.add_block_dot_answer(is_black, "green");
     }
 
     Ok(board)
diff --git a/cspuz_solver_backend/src/puzzle/norinori.rs b/cspuz_solver_backend/src/puzzle/norinori.rs
index d6ac4258..0b53910a 100644
--- a/cspuz_solver_backend/src/puzzle/norinori.rs
+++ b/cspuz_solver_backend/src/puzzle/norinori.rs
@@ -18,18 +18,7 @@ pub fn solve(url: &str) -> Result<Board, &'static str> {
     board.add_borders(&borders, "black");
 
     if let Some(is_black) = &ans {
-        for y in 0..height {
-            for x in 0..width {
-                if let Some(b) = is_black[y][x] {
-                    board.push(Item::cell(
-                        y,
-                        x,
-                        "green",
-                        if b { ItemKind::Block } else { ItemKind::Dot },
-                    ));
-                }
-            }
-        }
+        board.add_block_dot_answer(is_black, "green");
     }
 
     Ok(board)
diff --git a/cspuz_solver_backend/src/puzzle/nuritwin.rs b/cspuz_solver_backend/src/puzzle/nuritwin.rs
index 234a6283..be235edf 100644
--- a/cspuz_solver_backend/src/puzzle/nuritwin.rs
+++ b/cspuz_solver_backend/src/puzzle/nuritwin.rs
@@ -18,18 +18,7 @@ pub fn solve(url: &str) -> Result<Board, &'static str> {
     board.add_borders(&borders, "black");
 
     if let Some(is_black) = &ans {
-        for y in 0..height {
-            for x in 0..width {
-                if let Some(b) = is_black[y][x] {
-                    board.push(Item::cell(
-                        y,
-                        x,
-                        "green",
-                        if b { ItemKind::Block } else { ItemKind::Dot },
-                    ));
-                }
-            }
-        }
+        board.add_block_dot_answer(is_black, "green");
     }
     let rooms = graph::borders_to_rooms(&borders);
     assert_eq!(rooms.len(), clues.len());
diff --git a/cspuz_solver_backend/src/puzzle/shimaguni.rs b/cspuz_solver_backend/src/puzzle/shimaguni.rs
index eb438555..1df1a3a7 100644
--- a/cspuz_solver_backend/src/puzzle/shimaguni.rs
+++ b/cspuz_solver_backend/src/puzzle/shimaguni.rs
@@ -21,18 +21,7 @@ pub fn solve(url: &str) -> Result<Board, &'static str> {
     board.add_borders(&borders, "black");
 
     if let Some(is_black) = &is_black {
-        for y in 0..height {
-            for x in 0..width {
-                if let Some(b) = is_black[y][x] {
-                    board.push(Item::cell(
-                        y,
-                        x,
-                        "green",
-                        if b { ItemKind::Block } else { ItemKind::Dot },
-                    ));
-                }
-            }
-        }
+        board.add_block_dot_answer(is_black, "green");
     }
     let rooms = graph::borders_to_rooms(&borders);
     assert_eq!(rooms.len(), clues.len());
diff --git a/cspuz_solver_backend/src/puzzle/slitherlink.rs b/cspuz_solver_backend/src/puzzle/slitherlink.rs
index 9c9bb314..0afd283f 100644
--- a/cspuz_solver_backend/src/puzzle/slitherlink.rs
+++ b/cspuz_solver_backend/src/puzzle/slitherlink.rs
@@ -29,30 +29,7 @@ pub fn solve(url: &str) -> Result<Board, &'static str> {
         }
     }
     if let Some(is_line) = &is_line {
-        for y in 0..height {
-            for x in 0..=width {
-                if let Some(b) = is_line.vertical[y][x] {
-                    board.push(Item {
-                        y: y * 2 + 1,
-                        x: x * 2,
-                        color: "green",
-                        kind: if b { ItemKind::Wall } else { ItemKind::Cross },
-                    })
-                }
-            }
-        }
-        for y in 0..=height {
-            for x in 0..width {
-                if let Some(b) = is_line.horizontal[y][x] {
-                    board.push(Item {
-                        y: y * 2,
-                        x: x * 2 + 1,
-                        color: "green",
-                        kind: if b { ItemKind::Wall } else { ItemKind::Cross },
-                    })
-                }
-            }
-        }
+        board.add_grid_edges(is_line, "green", ItemKind::Wall, ItemKind::Cross);
     }
 
     Ok(board)
diff --git a/cspuz_solver_backend/src/puzzle/stostone.rs b/cspuz_solver_backend/src/puzzle/stostone.rs
index 6c4eb4d2..0a8d7b8f 100644
--- a/cspuz_solver_backend/src/puzzle/stostone.rs
+++ b/cspuz_solver_backend/src/puzzle/stostone.rs
@@ -21,18 +21,7 @@ pub fn solve(url: &str) -> Result<Board, &'static str> {
     board.add_borders(&borders, "black");
 
     if let Some(is_black) = &is_black {
-        for y in 0..height {
-            for x in 0..width {
-                if let Some(b) = is_black[y][x] {
-                    board.push(Item::cell(
-                        y,
-                        x,
-                        "green",
-                        if b { ItemKind::Block } else { ItemKind::Dot },
-                    ));
-                }
-            }
-        }
+        board.add_block_dot_answer(is_black, "green");
     }
     let rooms = graph::borders_to_rooms(&borders);
     assert_eq!(rooms.len(), clues.len());
diff --git a/cspuz_solver_backend/src/puzzle/yajilin_regions.rs b/cspuz_solver_backend/src/puzzle/yajilin_regions.rs
index dedd32f9..15ba1242 100644
--- a/cspuz_solver_backend/src/puzzle/yajilin_regions.rs
+++ b/cspuz_solver_backend/src/puzzle/yajilin_regions.rs
@@ -37,18 +37,7 @@ pub fn solve(url: &str) -> Result<Board, &'static str> {
     board.add_borders(&borders, "black");
 
     if let Some((ref is_line, ref is_black)) = ans {
-        for y in 0..height {
-            for x in 0..width {
-                if let Some(b) = is_black[y][x] {
-                    board.push(Item::cell(
-                        y,
-                        x,
-                        "green",
-                        if b { ItemKind::Block } else { ItemKind::Dot },
-                    ));
-                }
-            }
-        }
+        board.add_block_dot_answer(is_black, "green");
 
         let mut skip_line = vec![];
         for y in 0..height {