diff --git a/kifu/kifu-core/src/types.rs b/kifu/kifu-core/src/types.rs
index e37992a..9b4eea9 100644
--- a/kifu/kifu-core/src/types.rs
+++ b/kifu/kifu-core/src/types.rs
@@ -1,6 +1,6 @@
 use std::time::Duration;
 
-#[derive(Clone, Copy, Debug)]
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
 pub enum Color {
     Black,
     White,
diff --git a/kifu/kifu-core/src/ui/types.rs b/kifu/kifu-core/src/ui/types.rs
index 98bbaf1..f607356 100644
--- a/kifu/kifu-core/src/ui/types.rs
+++ b/kifu/kifu-core/src/ui/types.rs
@@ -1,12 +1,12 @@
 use crate::types::{Color, Size};
 
-#[derive(Clone, Copy, Debug)]
+#[derive(Clone, Copy, Debug, PartialEq)]
 pub struct Jitter {
     pub x: i8,
     pub y: i8,
 }
 
-#[derive(Clone, Copy, Debug)]
+#[derive(Clone, Copy, Debug, PartialEq)]
 pub struct StoneElement {
     pub color: Color,
     pub jitter: Jitter,
@@ -21,13 +21,13 @@ impl StoneElement {
     }
 }
 
-#[derive(Clone, Copy, Debug)]
+#[derive(Clone, Copy, Debug, PartialEq)]
 pub struct PlayStoneRequest {
     col: u8,
     row: u8,
 }
 
-#[derive(Clone, Copy, Debug)]
+#[derive(Clone, Copy, Debug, PartialEq)]
 pub enum IntersectionElement {
     Unplayable,
     Empty(PlayStoneRequest),
diff --git a/kifu/kifu-gtk/src/ui/board.rs b/kifu/kifu-gtk/src/ui/board.rs
index 20ae649..58ce1b1 100644
--- a/kifu/kifu-gtk/src/ui/board.rs
+++ b/kifu/kifu-gtk/src/ui/board.rs
@@ -131,7 +131,15 @@ impl ObjectImpl for BoardPrivate {
                 });
 
                 let cursor = cursor_location.borrow();
-                pen.ghost_stone(context, cursor.row, cursor.column, *current_player.borrow());
+                match board.stone(cursor.row, cursor.column) {
+                    IntersectionElement::Empty(_) => pen.ghost_stone(
+                        context,
+                        cursor.row,
+                        cursor.column,
+                        *current_player.borrow(),
+                    ),
+                    _ => {}
+                }
             });
 
         let motion_controller = gtk::EventControllerMotion::new();
diff --git a/kifu/kifu-gtk/src/ui/playing_field.rs b/kifu/kifu-gtk/src/ui/playing_field.rs
index 742754c..ac6708b 100644
--- a/kifu/kifu-gtk/src/ui/playing_field.rs
+++ b/kifu/kifu-gtk/src/ui/playing_field.rs
@@ -90,9 +90,13 @@ impl PlayingField {
 
 #[cfg(feature = "screenplay")]
 pub fn playing_field_view() -> PlayingFieldView {
-    let mut board = Board::default();
-    *board.stone_mut(4, 4) = Some(StoneElement::new(Color::White));
-    *board.stone_mut(15, 15) = Some(StoneElement::new(Color::Black));
+    let mut board = BoardElement::new(Size {
+        width: 19,
+        height: 19,
+    });
+    *board.stone_mut(4, 4) = IntersectionElement::Filled(StoneElement::new(Color::White));
+    *board.stone_mut(15, 15) = IntersectionElement::Filled(StoneElement::new(Color::Black));
+    *board.stone_mut(18, 18) = IntersectionElement::Unplayable;
     let player_card_black = PlayerCardElement {
         color: Color::Black,
         name: "Savanni".to_owned(),
diff --git a/rust-toolchain.toml b/rust-toolchain.toml
deleted file mode 100644
index 1cae25b..0000000
--- a/rust-toolchain.toml
+++ /dev/null
@@ -1,3 +0,0 @@
-[toolchain]
-channel = "1.68.2"
-components = ["rust-src"]