diff --git a/history/004_seasaw/src/main/java/com/github/drinkjava2/frog/Application.java b/history/004_seasaw/src/main/java/com/github/drinkjava2/frog/Application.java
new file mode 100644
index 0000000..768763f
--- /dev/null
+++ b/history/004_seasaw/src/main/java/com/github/drinkjava2/frog/Application.java
@@ -0,0 +1,88 @@
+package com.github.drinkjava2.frog;
+
+import java.awt.event.ActionEvent;
+import java.awt.event.ActionListener;
+import java.io.File;
+
+import javax.swing.JButton;
+import javax.swing.JFrame;
+
+import com.github.drinkjava2.frog.brain.BrainPicture;
+
+/**
+ * Application's main method start the program
+ * 
+ * @author Yong Zhu
+ * @since 1.0
+ */
+public class Application {
+	/** SHOW first frog's brain structure */
+	public static boolean SHOW_FIRST_FROG_BRAIN = false;
+	public static final String CLASSPATH;
+
+	static {
+		String classpath = new File("").getAbsolutePath();
+		int i = classpath.lastIndexOf("\\frog\\");
+		if (i > 0)
+			CLASSPATH = classpath.substring(0, i) + "\\frog\\";// windows
+		else
+			CLASSPATH = classpath + "/"; // UNIX
+	}
+	public static JFrame mainFrame = new JFrame();
+	public static Env env = new Env();
+	public static BrainPicture brainPic = new BrainPicture(Env.ENV_WIDTH + 5, 0, Env.FROG_BRAIN_WIDTH,
+			Env.FROG_BRAIN_DISP_WIDTH);
+
+	public static void main(String[] args) throws InterruptedException {
+		mainFrame.setLayout(null);
+		mainFrame.setSize(Env.ENV_WIDTH + 20, Env.ENV_HEIGHT + 100); // 窗口大小
+		mainFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); // 关闭时退出程序
+		mainFrame.add(env);
+
+		mainFrame.add(brainPic);
+
+		JButton button = new JButton("Show first frog's brain");
+		int buttonWidth = 180;
+		int buttonHeight = 22;
+		int buttonXpos = Env.ENV_WIDTH / 2 - buttonWidth / 2;
+		button.setBounds(buttonXpos, Env.ENV_HEIGHT + 8, buttonWidth, buttonHeight);
+		ActionListener al = new ActionListener() {
+			@Override
+			public void actionPerformed(ActionEvent arg0) {
+				SHOW_FIRST_FROG_BRAIN = !SHOW_FIRST_FROG_BRAIN;
+				if (SHOW_FIRST_FROG_BRAIN) {
+					button.setText("Hide first frog's brain");
+					int y = Env.ENV_HEIGHT + 100;
+					if (Env.FROG_BRAIN_DISP_WIDTH + 41 > y)
+						y = Env.FROG_BRAIN_DISP_WIDTH + 41;
+					mainFrame.setSize(Env.ENV_WIDTH + Env.FROG_BRAIN_DISP_WIDTH + 25, y);
+				} else {
+					button.setText("Show first frog's brain");
+					mainFrame.setSize(Env.ENV_WIDTH + 20, Env.ENV_HEIGHT + 100);
+				}
+			}
+		};
+		button.addActionListener(al);
+		mainFrame.add(button);
+
+		JButton stopButton = new JButton("Pause");
+		stopButton.setBounds(buttonXpos, Env.ENV_HEIGHT + 35, buttonWidth, buttonHeight);
+		ActionListener a2 = new ActionListener() {
+			@Override
+			public void actionPerformed(ActionEvent arg0) {
+				Env.pause = !Env.pause;
+				if (Env.pause) {
+					stopButton.setText("Resume");
+				} else {
+					stopButton.setText("Pause");
+				}
+			}
+		};
+		stopButton.addActionListener(a2);
+		mainFrame.add(stopButton);
+
+		mainFrame.setVisible(true);
+		env.run();
+	}
+
+}