diff --git a/docs/坦克大战笔记.docx b/docs/坦克大战笔记.docx
index 6db9858..0d77952 100644
Binary files a/docs/坦克大战笔记.docx and b/docs/坦克大战笔记.docx differ
diff --git a/src/com/demo/tank/coruse2/Tank.java b/src/com/demo/tank/coruse2/Tank.java
index 1631cd9..7f6ee56 100644
--- a/src/com/demo/tank/coruse2/Tank.java
+++ b/src/com/demo/tank/coruse2/Tank.java
@@ -15,7 +15,10 @@ public class Tank {
     }
 
     public void paint(Graphics g) {
+        Color color = g.getColor();
+        g.setColor(Color.YELLOW);
         g.fillRect(x, y,50,50);
+        g.setColor(color);
         move();
     }
 
diff --git a/src/com/demo/tank/coruse2/TankFrame.java b/src/com/demo/tank/coruse2/TankFrame.java
index 119d6d5..5220bc8 100644
--- a/src/com/demo/tank/coruse2/TankFrame.java
+++ b/src/com/demo/tank/coruse2/TankFrame.java
@@ -7,12 +7,16 @@ import java.awt.event.WindowAdapter;
 import java.awt.event.WindowEvent;
 
 public class TankFrame extends Frame {
+    private static final int GAME_WIDTH = 800;
+    private static final int GAME_HEIGHT = 600;
+    Image image = null;
+
     Tank tank = new Tank(500, 500, Direction.UP);
     Bullet bullet = new Bullet(520, 440, Direction.UP);
 
     public TankFrame(){
         setVisible(true);
-        setSize(800, 600);
+        setSize(GAME_WIDTH, GAME_HEIGHT);
         setResizable(false);
         setTitle("tank war");
         this.addKeyListener(new MyKeyListener());
@@ -24,6 +28,20 @@ public class TankFrame extends Frame {
         });
     }
 
+    @Override
+    public void update(Graphics g) {
+        if(image == null){
+            image = this.createImage(GAME_WIDTH, GAME_HEIGHT);
+        }
+        Graphics imgGraphic =  image.getGraphics();
+        Color color = g.getColor();
+        imgGraphic.setColor(Color.WHITE);
+        imgGraphic.fillRect(0,0, GAME_WIDTH, GAME_HEIGHT);
+        imgGraphic.setColor(color);
+        paint(imgGraphic);
+        g.drawImage(image, 0, 0, null);
+    }
+
     @Override
     public void paint(Graphics g){
         tank.paint(g);