diff --git a/src/main.rs b/src/main.rs
index 7f6d901..aa13a50 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -7,8 +7,9 @@ struct Apr {
     col: i32,
     board: Vec<Vec<u8>>,
     grid: Mesh,
+    should_update_grid: bool,
     // Your state here...
-    __TEST_state : usize
+    __TEST_state: usize
 }
 
 fn make_grid(ctx: &mut Context, r: i32, c: i32, board: &[Vec<u8>]) -> GameResult<Mesh> {
@@ -65,13 +66,14 @@ impl Apr {
             col: c,
             grid: make_grid(_ctx, r, c, board.as_slice()).unwrap(),
             board: board,
-            __TEST_state : 0,
+            should_update_grid: false,
+            __TEST_state: 0,
         }
     }
 
-    fn set_colour(&mut self, ctx : &mut Context, r : usize, c : usize, col : u8) -> GameResult<()> {
+    fn set_colour(&mut self, r : usize, c : usize, col : u8) -> GameResult<()> {
         self.board[r][c] = col;
-        self.grid = make_grid(ctx, self.row, self.col, self.board.as_slice())?;
+        self.should_update_grid = true;
         Ok(())
     }
 }
@@ -83,7 +85,7 @@ impl EventHandler for Apr {
         for x in 0..self.row*self.col/5 {
             let c = self.__TEST_state % self.col as usize;
             let r = (self.__TEST_state / self.row as usize) % self.row as usize;
-            self.set_colour(_ctx, r, c, (self.board[r][c] + 1) % 8)?;
+            self.set_colour(r, c, (self.board[r][c] + 1) % 8)?;
             self.__TEST_state += 1;
         }
         Ok(())
@@ -93,6 +95,10 @@ impl EventHandler for Apr {
         graphics::clear(ctx, Color::new(0.5, 0.5, 0.5, 1.0));
         let drawparams = graphics::DrawParam::new();
 
+        if self.should_update_grid {
+            self.grid = make_grid(ctx, self.row, self.col, self.board.as_slice())?;
+            self.should_update_grid = false;
+        }
         graphics::draw(ctx, &self.grid, drawparams)?;
         // Draw code here...
         graphics::present(ctx)