diff --git a/makefile b/makefile
index e246b5b..5b1c9b4 100644
--- a/makefile
+++ b/makefile
@@ -15,17 +15,17 @@ SRC=\
 	nasal_dbg.h\
 	nasal.h
 
-STD=-std=c++11
+STD=14
 
 nasal:$(SRC)
-	$(CXX) $(STD) -O3 main.cpp -o nasal -fno-exceptions -ldl -Wshadow -Wall
+	$(CXX) -std=c++$(STD) -O3 main.cpp -o nasal -fno-exceptions -ldl -Wshadow -Wall
 nasal.exe:$(SRC)
-	$(CXX) $(STD) -O3 main.cpp -o nasal.exe -fno-exceptions -Wshadow -Wall -static
+	$(CXX) -std=c++$(STD) -O3 main.cpp -o nasal.exe -fno-exceptions -Wshadow -Wall -static
 
 stable-release:$(SRC)
-	$(CXX) $(STD) -O2 main.cpp -o nasal -fno-exceptions -ldl -Wshadow -Wall
+	$(CXX) -std=c++$(STD) -O2 main.cpp -o nasal -fno-exceptions -ldl -Wshadow -Wall
 stable-release-mingw:$(SRC)
-	$(CXX) $(STD) -O2 main.cpp -o nasal.exe -fno-exceptions -Wshadow -Wall -static
+	$(CXX) -std=c++$(STD) -O2 main.cpp -o nasal.exe -fno-exceptions -Wshadow -Wall -static
 
 test:nasal
 	@ ./nasal -o -e test/ascii-art.nas
diff --git a/module/makefile b/module/makefile
index f8b1dd7..234a28d 100644
--- a/module/makefile
+++ b/module/makefile
@@ -1,31 +1,31 @@
 .PHONY=clean all mingw-all
 
-CPPSTANDARD=-std=c++11
+STD=14
 
 libfib.so: fib.cpp
-	$(CXX) $(CPPSTANDARD) -c -O3 fib.cpp -fPIC -o fib.o
+	$(CXX) -std=c++$(STD) -c -O3 fib.cpp -fPIC -o fib.o
 	$(CXX) -shared -o libfib.so fib.o
 	rm fib.o
 libfib.dll: fib.cpp
-	$(CXX) $(CPPSTANDARD) -c -O3 fib.cpp -fPIC -o fib.o
+	$(CXX) -std=c++$(STD) -c -O3 fib.cpp -fPIC -o fib.o
 	$(CXX) -shared -o libfib.dll fib.o
 	del fib.o
 
 libkey.so: keyboard.cpp
-	$(CXX) $(CPPSTANDARD) -c -O3 keyboard.cpp -fPIC -o keyboard.o
+	$(CXX) -std=c++$(STD) -c -O3 keyboard.cpp -fPIC -o keyboard.o
 	$(CXX) -shared -o libkey.so keyboard.o
 	rm keyboard.o
 libkey.dll: keyboard.cpp
-	$(CXX) $(CPPSTANDARD) -c -O3 keyboard.cpp -fPIC -o keyboard.o -static
+	$(CXX) -std=c++$(STD) -c -O3 keyboard.cpp -fPIC -o keyboard.o -static
 	$(CXX) -shared -o libkey.dll keyboard.o -static
 	del keyboard.o
 
 libnasock.so: nasocket.cpp
-	$(CXX) $(CPPSTANDARD) -c -O3 nasocket.cpp -fPIC -o nasocket.o
+	$(CXX) -std=c++$(STD) -c -O3 nasocket.cpp -fPIC -o nasocket.o
 	$(CXX) -shared -o libnasock.so nasocket.o
 	rm nasocket.o
 libnasock.dll: nasocket.cpp
-	$(CXX) $(CPPSTANDARD) -c -O3 nasocket.cpp -fPIC -o nasocket.o -lwsock32 -static
+	$(CXX) -std=c++$(STD) -c -O3 nasocket.cpp -fPIC -o nasocket.o -lwsock32 -static
 	$(CXX) -shared -o libnasock.dll nasocket.o -lwsock32 -static
 	del nasocket.o
 
diff --git a/nasal_builtin.h b/nasal_builtin.h
index 182e52c..efea11c 100644
--- a/nasal_builtin.h
+++ b/nasal_builtin.h
@@ -389,7 +389,10 @@ nas_ref builtin_die(nas_ref* local,nasal_gc& gc)
     nas_ref str=local[1];
     if(str.type!=vm_str)
         return nas_err("die","\"str\" must be string");
-    std::cerr<<"[vm] error: "<<str.str()<<'\n';
+    std::cerr<<bold_cyan<<"[vm] "
+             <<bold_red<<"error: "
+             <<bold_white<<str.str()<<'\n'
+             <<reset;
     return {vm_none};
 }
 nas_ref builtin_find(nas_ref* local,nasal_gc& gc)
diff --git a/nasal_err.h b/nasal_err.h
index 2f6d69c..943441d 100644
--- a/nasal_err.h
+++ b/nasal_err.h
@@ -8,8 +8,61 @@
 
 #ifdef _WIN32
 #include <windows.h> // use SetConsoleTextAttribute
+struct for_reset
+{
+    CONSOLE_SCREEN_BUFFER_INFO scr;
+    for_reset(){
+        GetConsoleScreenBufferInfo(GetStdHandle(STD_OUTPUT_HANDLE),&scr);
+    }
+}reset_ter_color;
 #endif
 
+std::ostream& bold_red(std::ostream& s)
+{
+#ifdef _WIN32
+    SetConsoleTextAttribute(GetStdHandle(STD_OUTPUT_HANDLE),0x0c);
+#else
+    s<<"\033[91;1m";
+#endif
+    return s;
+}
+std::ostream& bold_cyan(std::ostream& s)
+{
+#ifdef _WIN32
+    SetConsoleTextAttribute(GetStdHandle(STD_OUTPUT_HANDLE),0x03);
+#else
+    s<<"\033[36;1m";
+#endif
+    return s;
+}
+std::ostream& bold_orange(std::ostream& s)
+{
+#ifdef _WIN32
+    SetConsoleTextAttribute(GetStdHandle(STD_ERROR_HANDLE),0x0e);
+#else
+    s<<"\033[93;1m";
+#endif
+    return s;
+}
+std::ostream& bold_white(std::ostream& s)
+{
+#ifdef _WIN32
+    SetConsoleTextAttribute(GetStdHandle(STD_ERROR_HANDLE),0x0f);
+#else
+    s<<"\033[0m\033[1m";
+#endif
+    return s;
+}
+std::ostream& reset(std::ostream& s)
+{
+#ifdef _WIN32
+    SetConsoleTextAttribute(GetStdHandle(STD_OUTPUT_HANDLE),reset_ter_color.scr.wAttributes);
+#else
+    s<<"\033[0m";
+#endif
+    return s;
+}
+
 class fstreamline
 {
 protected:
@@ -18,14 +71,13 @@ protected:
 public:
     void load(const string& f)
     {
-        if(file==f) // don't need to load a loaded file
-            return;
+        if(file==f) return; // don't need to load a loaded file
         file=f;
         res.clear();
         std::ifstream fin(f,std::ios::binary);
         if(fin.fail())
         {
-            std::cerr<<"[src] cannot open file <"<<f<<">\n";
+            std::cerr<<bold_cyan<<"[src] "<<reset<<"cannot open file <"<<f<<">\n";
             std::exit(1);
         }
         string line;
@@ -49,45 +101,30 @@ class nasal_err:public fstreamline
 {
 private:
     u32 error;
-    void printstg(const char* stage)
-    {
-#ifdef _WIN32
-        CONSOLE_SCREEN_BUFFER_INFO scrinfo;
-        GetConsoleScreenBufferInfo(GetStdHandle(STD_ERROR_HANDLE),&scrinfo);
-        SetConsoleTextAttribute(GetStdHandle(STD_ERROR_HANDLE),0x03);
-        std::cerr<<"[";
-        SetConsoleTextAttribute(GetStdHandle(STD_ERROR_HANDLE),0x0c);
-        std::cerr<<stage;
-        SetConsoleTextAttribute(GetStdHandle(STD_ERROR_HANDLE),0x03);
-        std::cerr<<"] ";
-        SetConsoleTextAttribute(GetStdHandle(STD_ERROR_HANDLE),scrinfo.wAttributes);
-#else
-        std::cerr<<"\033[36m[\033[91m"<<stage<<"\033[36m]\033[0m ";
-#endif
-    }
 public:
     nasal_err():error(0){}
     void err(const char* stage,const string& info)
     {
         ++error;
-        printstg(stage);
-        std::cerr<<info<<"\n";
+        std::cerr<<bold_cyan<<"["<<stage<<"] "<<reset<<info<<"\n";
     }
     void err(const char* stage,u32 line,u32 column,const string& info)
     {
         ++error;
         const string& code=res[line-1];
-        printstg(stage);
-        std::cerr<<file<<":"<<line<<":"<<column<<" "<<info<<"\n"<<code<<"\n";
+        std::cerr<<bold_cyan<<"["<<stage<<"] "
+                 <<bold_orange<<file<<":"<<line<<":"<<column<<" "
+                 <<bold_white<<info<<reset<<"\n"<<code<<"\n";
         for(i32 i=0;i<(i32)column-1;++i)
             std::cerr<<char(" \t"[code[i]=='\t']);
-        std::cerr<<"^\n";
+        std::cerr<<bold_red<<"^\n"<<reset;
     }
     void err(const char* stage,u32 line,const string& info)
     {
         ++error;
-        printstg(stage);
-        std::cerr<<file<<":"<<line<<" "<<info<<"\n"<<res[line-1]<<'\n';
+        std::cerr<<bold_cyan<<"["<<stage<<"] "
+                 <<bold_orange<<file<<":"<<line<<" "
+                 <<bold_white<<info<<reset<<"\n"<<res[line-1]<<'\n';
     }
     void chkerr(){if(error)std::exit(1);}
 };
diff --git a/nasal_gc.h b/nasal_gc.h
index 0597222..8ecda75 100644
--- a/nasal_gc.h
+++ b/nasal_gc.h
@@ -4,6 +4,8 @@
 #include <queue>
 #include <unordered_map>
 
+#include "nasal_err.h"
+
 enum vm_type:u8{
     /* none-gc object */
     vm_none=0,
@@ -721,7 +723,10 @@ void nasal_gc::ctxreserve()
 // use to print error log and return error value
 nas_ref nas_err(const string& err_f,const string& info)
 {
-    std::cerr<<"[vm] "<<err_f<<": "<<info<<"\n";
+    std::cerr<<bold_cyan<<"[vm] "
+             <<bold_red<<err_f<<": "
+             <<bold_white<<info<<"\n"
+             <<reset;
     return {vm_none};
 }
 #endif
\ No newline at end of file
diff --git a/nasal_vm.h b/nasal_vm.h
index b378d59..49e9004 100644
--- a/nasal_vm.h
+++ b/nasal_vm.h
@@ -4,6 +4,8 @@
 #include <iomanip>
 #include <stack>
 
+#include "nasal_err.h"
+
 class nasal_vm
 {
 protected:
@@ -207,8 +209,9 @@ void nasal_vm::bytecodeinfo(const char* header,const u32 p)
 void nasal_vm::traceback()
 {
     nas_ref* bottom=stack+bytecode[0].num; // bytecode[0] is op_intg
+    nas_ref* main_ctx_top=gc.stack==stack?top:gc.mctx.top; // if error occurs in coroutine, this works
     std::stack<u32> ret;
-    for(nas_ref* i=bottom;i<=top;++i)
+    for(nas_ref* i=bottom;i<=main_ctx_top;++i)
         if(i->type==vm_ret)
             ret.push(i->ret());
     ret.push(pc); // store the position program crashed
@@ -314,7 +317,10 @@ void nasal_vm::detail()
 [[noreturn]]
 void nasal_vm::die(const string& str)
 {
-    std::cout<<"[vm] "<<str<<"\n";
+    std::cout<<bold_cyan<<"[vm] "
+             <<bold_red<<"error: "
+             <<bold_white<<str<<"\n"
+             <<reset;
     traceback();
     stackinfo();
     if(detail_info)