diff --git a/docs/坦克大战笔记.docx b/docs/坦克大战笔记.docx
index fe01a06..2cb4723 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/course4/Bullet.java b/src/com/demo/tank/course4/Bullet.java
index 392ced0..cda1cdc 100644
--- a/src/com/demo/tank/course4/Bullet.java
+++ b/src/com/demo/tank/course4/Bullet.java
@@ -11,6 +11,7 @@ public class Bullet {
     private boolean live = true;
     private Group group = Group.BAD;
     private TankFrameV4 tf;
+    Rectangle rect = new Rectangle();
 
     public Bullet(int x, int y, Direction direction, Group group, TankFrameV4 tf) {
         this.x = x;
@@ -18,6 +19,11 @@ public class Bullet {
         this.direction = direction;
         this.group = group;
         this.tf = tf;
+
+        rect.x = this.x;
+        rect.y = this.y;
+        rect.width = Bullet.WIDTH;
+        rect.height = Bullet.HEIGHT;
     }
 
     public void paint(Graphics g){
@@ -57,15 +63,15 @@ public class Bullet {
         if(x < 0 || y < 0 || x > TankFrameV4.GAME_WIDTH || y > TankFrameV4.GAME_HEIGHT){
             live = false;
         }
+        rect.x = this.x;
+        rect.y = this.y;
     }
 
     //检测是否跟坦克碰撞
     public void collideWith(Tank tank){
         //关闭队友伤害
         if(this.group == tank.getGroup()) return;
-        Rectangle bulletRect = new Rectangle(x, y, WIDTH, HEIGHT);
-        Rectangle tankRect = new Rectangle(tank.getX(), tank.getY(), Tank.WIDTH, Tank.HEIGHT);
-        if(bulletRect.intersects(tankRect)){
+        if(rect.intersects(tank.rect)){
             tank.die();
             this.die();
             //爆炸
diff --git a/src/com/demo/tank/course4/Tank.java b/src/com/demo/tank/course4/Tank.java
index 51c840f..a845e23 100644
--- a/src/com/demo/tank/course4/Tank.java
+++ b/src/com/demo/tank/course4/Tank.java
@@ -14,6 +14,7 @@ public class Tank {
     public static final int WIDTH = ResourceManager.tankD.getWidth();
     public static final int HEIGHT = ResourceManager.tankD.getHeight();
     private Random random = new Random();
+    Rectangle rect = new Rectangle();
 
     public Tank(int x, int y, Direction dir, Group group, TankFrameV4 tankFrame) {
         this.x = x;
@@ -21,6 +22,11 @@ public class Tank {
         this.dir = dir;
         this.group = group;
         this.tankFrame = tankFrame;
+
+        rect.x = this.x;
+        rect.y = this.y;
+        rect.width = Tank.WIDTH;
+        rect.height = Tank.HEIGHT;
     }
 
     public void paint(Graphics g) {
@@ -69,6 +75,9 @@ public class Tank {
 
         //边界检测
         boundsCheck();
+
+        rect.x = this.x;
+        rect.y = this.y;
     }
 
     private void boundsCheck() {