diff --git a/kifu/kifu-gtk/src/ui/board.rs b/kifu/kifu-gtk/src/ui/board.rs
index 4ededd6..7b442f5 100644
--- a/kifu/kifu-gtk/src/ui/board.rs
+++ b/kifu/kifu-gtk/src/ui/board.rs
@@ -15,6 +15,7 @@ use std::{cell::RefCell, io::Cursor, rc::Rc};
 
 const WIDTH: i32 = 800;
 const HEIGHT: i32 = 800;
+const MARGIN: i32 = 20;
 
 #[derive(Clone, Default, PartialEq)]
 struct Addr {
@@ -84,6 +85,7 @@ impl ObjectImpl for BoardPrivate {
             .set_draw_func(move |_, context, width, height| {
                 let render_start = std::time::Instant::now();
                 let board = board.borrow();
+
                 match background {
                     Ok(Some(ref background)) => {
                         context.set_source_pixbuf(&background, 0., 0.);
@@ -99,20 +101,32 @@ impl ObjectImpl for BoardPrivate {
                 let vspace_between = ((height - 40) as f64) / ((board.size.height - 1) as f64);
 
                 let pen = Pen {
-                    x_offset: 20.,
-                    y_offset: 20.,
+                    x_offset: MARGIN as f64,
+                    y_offset: MARGIN as f64,
                     hspace_between,
                     vspace_between,
                 };
 
                 (0..board.size.width).for_each(|col| {
-                    context.move_to(20.0 + (col as f64) * hspace_between, 20.0);
-                    context.line_to(20.0 + (col as f64) * hspace_between, (height as f64) - 20.0);
+                    context.move_to(
+                        (MARGIN as f64) + (col as f64) * hspace_between,
+                        MARGIN as f64,
+                    );
+                    context.line_to(
+                        (MARGIN as f64) + (col as f64) * hspace_between,
+                        (height as f64) - (MARGIN as f64),
+                    );
                     let _ = context.stroke();
                 });
                 (0..board.size.height).for_each(|row| {
-                    context.move_to(20.0, 20.0 + (row as f64) * vspace_between);
-                    context.line_to((width - 20) as f64, 20.0 + (row as f64) * vspace_between);
+                    context.move_to(
+                        MARGIN as f64,
+                        (MARGIN as f64) + (row as f64) * vspace_between,
+                    );
+                    context.line_to(
+                        (width - MARGIN) as f64,
+                        (MARGIN as f64) + (row as f64) * vspace_between,
+                    );
                     let _ = context.stroke();
                 });
 
@@ -162,15 +176,18 @@ impl ObjectImpl for BoardPrivate {
                 let hspace_between = ((WIDTH - 40) as f64) / ((board.size.width - 1) as f64);
                 let vspace_between = ((HEIGHT - 40) as f64) / ((board.size.height - 1) as f64);
 
-                let addr =
-                    if x.round() < 20. || x.round() > 780. || y.round() < 20. || y.round() > 780. {
-                        None
-                    } else {
-                        Some(Addr {
-                            column: ((x.round() - 20.) / hspace_between).round() as u8,
-                            row: ((y.round() - 20.) / vspace_between).round() as u8,
-                        })
-                    };
+                let addr = if x.round() < MARGIN as f64
+                    || x.round() > (WIDTH - MARGIN) as f64
+                    || y.round() < MARGIN as f64
+                    || y.round() > (HEIGHT - MARGIN) as f64
+                {
+                    None
+                } else {
+                    Some(Addr {
+                        column: ((x.round() - MARGIN as f64) / hspace_between).round() as u8,
+                        row: ((y.round() - MARGIN as f64) / vspace_between).round() as u8,
+                    })
+                };
 
                 if *cursor != addr.clone() {
                     *cursor = addr;
@@ -246,7 +263,7 @@ impl Pen {
         context.arc(
             self.x_offset + (col as f64) * self.hspace_between,
             self.y_offset + (row as f64) * self.vspace_between,
-            10.,
+            5.,
             0.,
             2. * std::f64::consts::PI,
         );
@@ -258,14 +275,7 @@ impl Pen {
             Color::White => context.set_source_rgb(0.9, 0.9, 0.9),
             Color::Black => context.set_source_rgb(0.0, 0.0, 0.0),
         };
-        context.arc(
-            20.0 + (col as f64) * self.hspace_between,
-            20.0 + (row as f64) * self.vspace_between,
-            25.0,
-            0.0,
-            2.0 * std::f64::consts::PI,
-        );
-        let _ = context.fill();
+        self.draw_stone(context, row, col);
     }
 
     fn ghost_stone(&self, context: &cairo::Context, row: u8, col: u8, color: Color) {
@@ -273,10 +283,15 @@ impl Pen {
             Color::White => context.set_source_rgba(0.9, 0.9, 0.9, 0.5),
             Color::Black => context.set_source_rgba(0.0, 0.0, 0.0, 0.5),
         };
+        self.draw_stone(context, row, col);
+    }
+
+    fn draw_stone(&self, context: &cairo::Context, row: u8, col: u8) {
+        let radius = self.hspace_between / 2. - 2.;
         context.arc(
-            20.0 + (col as f64) * self.hspace_between,
-            20.0 + (row as f64) * self.vspace_between,
-            25.0,
+            self.x_offset + (col as f64) * self.hspace_between,
+            self.y_offset + (row as f64) * self.vspace_between,
+            radius,
             0.0,
             2.0 * std::f64::consts::PI,
         );