increment i by 1 for summing values

src/logic/future_moves.rs

@@ -200,7 +200,7 @@ impl FutureMoves {
                     .rev() // rev then reverse so we get an index starting from the back
                     .enumerate()
                     // since children are sorted by value, we should weight the first one more
-                    .map(|(i, &child)| self.arena[child].value * (i as i128))
+                    .map(|(i, &child)| self.arena[child].value * ((i + 1) as i128))
                     .sum::<i128>();
 
                 self.arena[idx].value =