fix

js/interactive_grid.js

@@ -107,7 +107,7 @@ function drawGridAfter() {
             ctx_aft.lineWidth = 2;
             ctx_aft.stroke();
 
-            if (grid[row][col]) {
+            if (grid_aft[row][col]) {
                 ctx_aft.fillStyle = 'rgba(0, 255, 0, 0.5)';
                 ctx_aft.fillRect(col * cellSize, row * cellSize, cellSize, cellSize);
             }