diff --git a/doc/README_zh.md b/doc/README_zh.md
index 43bbaa3..7c02eb2 100644
--- a/doc/README_zh.md
+++ b/doc/README_zh.md
@@ -19,7 +19,7 @@
 * [__开发历史__](../doc/dev_zh.md)
 * [__测试数据__](../doc/benchmark.md)
 * [__特殊之处__](#与andy解释器的不同之处)
-* [__堆栈追踪信息__](#trace-back-info)
+* [__堆栈追踪信息__](#堆栈追踪信息)
 * [__调试器__](#调试器)
 
 __如果有好的意见或建议，欢迎联系我们!__
diff --git a/doc/nasal-http-test-web.html b/doc/nasal-http-test-web.html
index a4f8307..0119175 100644
--- a/doc/nasal-http-test-web.html
+++ b/doc/nasal-http-test-web.html
@@ -51,7 +51,7 @@
             <p>
                 The interpreter is totally rewritten by <a href="https://github.com/ValKmjolnir">ValKmjolnir</a> using C++(-std=c++11) without reusing the code in Andy Ross's nasal interpreter.
                 But we really appreciate that Andy created this amazing programming language and his interpreter project.
-                Now this project uses <a href="/license">GPL-2.0 license</a> (2021/5/4).<br/>
+                Now this project uses <a href="/license">GPL-2.0 license</a>.<br/>
             </p>
             <p>
                 这个解释器是由<a href="https://github.com/ValKmjolnir">ValKmjolnir</a>用C++11编写的，完全没有复用Andy Ross版解释器的代码。但是我们仍然非常感谢Andy为我们带来了这么一款有趣的编程语言。
@@ -71,14 +71,21 @@
                 nasal运行brainfuck绘制的曼德勃罗集合(右)。
             </p>
             <p>
-                Nasal can run this test file(test/bfcolored.nas) to draw this picture in about 220 seconds.
+                Nasal can run this test file(test/bf.nas) to draw this picture in about 220 seconds.
                 In fact this test file cost over 2200 seconds before ver 8.0 .
             </p>
             <p>
-                Nasal现在可以在220秒内运行该文件(test/bfcolored.nas)并绘制出这张图。
+                Nasal现在可以在220秒内运行该文件(test/bf.nas)并绘制出这张图。
                 在8.0版本中这个解释器需要跑超过2200秒来绘制这张图。
             </p>
+            <p>
+                The figure below is the feigenbaum-figure generated by ppm script written in nasal.
+            </p>
+            <p>
+                下方是使用 nasal 的 ppm 生成脚本生成的 feigenbaum 图形。
+            </p>
         </text>
+        <img src="/doc/pic/feigenbaum.png" width="900" height="550" style="margin-left: 15px;"><br /></img>
         <h2>&nbsp;Example | 样例代码</h2>
         <form method="get">
             <text style="margin-left: 15px;"> </text>
diff --git a/doc/pic/feigenbaum.png b/doc/pic/feigenbaum.png
new file mode 100644
index 0000000..50c3929
Binary files /dev/null and b/doc/pic/feigenbaum.png differ
diff --git a/src/nasal_builtin.cpp b/src/nasal_builtin.cpp
index 73a90c7..93eb303 100644
--- a/src/nasal_builtin.cpp
+++ b/src/nasal_builtin.cpp
@@ -369,16 +369,16 @@ var builtin_find(var* local, gc& ngc) {
 
 var builtin_type(var* local, gc& ngc) {
     switch(local[1].type) {
-        case vm_none: return ngc.newstr("undefined");break;
-        case vm_nil:  return ngc.newstr("nil");      break;
-        case vm_num:  return ngc.newstr("num");      break;
-        case vm_str:  return ngc.newstr("str");      break;
-        case vm_vec:  return ngc.newstr("vec");      break;
-        case vm_hash: return ngc.newstr("hash");     break;
-        case vm_func: return ngc.newstr("func");     break;
-        case vm_obj:  return ngc.newstr("obj");      break;
-        case vm_co:   return ngc.newstr("coroutine");break;
-        case vm_map:  return ngc.newstr("mapper");   break;
+        case vm_none: return ngc.newstr("undefined");
+        case vm_nil: return ngc.newstr("nil");
+        case vm_num: return ngc.newstr("num");
+        case vm_str: return ngc.newstr("str");
+        case vm_vec: return ngc.newstr("vec");
+        case vm_hash: return ngc.newstr("hash");
+        case vm_func: return ngc.newstr("func");
+        case vm_obj: return ngc.newstr("obj");
+        case vm_co: return ngc.newstr("coroutine");
+        case vm_map: return ngc.newstr("namespace");
     }
     return nil;
 }
diff --git a/test/feigenbaum.nas b/test/feigenbaum.nas
new file mode 100644
index 0000000..6f1535d
--- /dev/null
+++ b/test/feigenbaum.nas
@@ -0,0 +1,48 @@
+import.std.process_bar;
+
+var ppm=func(filename, width, height, RGB){
+    # P3 use ASCII number
+    # P6 use binary character
+    var fd = io.open(filename, "wb");
+    io.write(fd, "P6\n"~width~" "~height~"\n255\n");
+    for(var i = 0; i<height; i+=1) {
+        for(var j = 0; j<width; j+=1) {
+            io.write(fd, RGB(i, j));
+        }
+    }
+    io.close(fd);
+}
+
+var width = 1600;
+var height = 900;
+var bar=(os.platform()=="windows")?
+    process_bar.bar(front:"sharp",back:"point",sep:"line",length:50):
+    process_bar.high_resolution_bar(50);
+
+var RGB = func(h, w) {
+    var r = 2+w*2/width;
+    var x = (height-h)/height;
+
+    var res = 0;
+    var tmp = 0.5;
+    for(var i = 0; i<50; i+=1) {
+        tmp = r*tmp*(1-tmp);
+    }
+    for(var i = 0; i<100; i+=1) {
+        tmp = r*tmp*(1-tmp);
+        if (math.abs(tmp-x)<0.001) {
+            res = 255;
+            break;
+        }
+    }
+
+    var progress = (h*width+w+1)/(width*height);
+    if(progress*100-int(progress*100)==0){
+        print(bar.bar(progress), " ", progress*100, "%          \r");
+    }
+
+    var c = char(res);
+    return c~c~c;
+}
+ppm("feigenbaum.ppm", width, height, RGB);
+println();
\ No newline at end of file
diff --git a/test/httptest.nas b/test/httptest.nas
index f3f66f7..d471e5a 100644
--- a/test/httptest.nas
+++ b/test/httptest.nas
@@ -314,7 +314,10 @@ while(1){
             http.send(client,respond.ok(io.readfile("./doc/pic/favicon.ico")));
         elsif(path=="/license")
             http.send(client,respond.ok(io.readfile("./LICENSE")));
-        elsif(path=="/doc/pic/nasal.png" or path=="/doc/pic/benchmark.png" or path=="/doc/pic/mandelbrot.png")
+        elsif(path=="/doc/pic/nasal.png" or
+            path=="/doc/pic/benchmark.png" or
+            path=="/doc/pic/mandelbrot.png" or
+            path=="/doc/pic/feigenbaum.png")
             http.send(client,respond.ok(io.readfile("."~path)));
         else{
             var filename=substr(path,1,size(path)-1);