diff --git a/src/main.cpp b/src/main.cpp
index d9e7588..16435b0 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -30,6 +30,7 @@ const u32 VM_SYMINFO   = 1<<7;
 const u32 VM_PROFILE   = 1<<8;
 const u32 VM_PROF_ALL  = 1<<9;
 const u32 VM_REF_FILE  = 1<<10;
+const u32 VM_LIMIT     = 1<<11;
 
 std::ostream& help(std::ostream& out) {
     out
@@ -59,6 +60,7 @@ std::ostream& help(std::ostream& out) {
     << "         --prof     | show profiling result, available in debug mode.\n"
     << "         --prof-all | show profiling result of all files,"
     << "available under debug mode.\n"
+    << "         --limit    | use limited execution mode."
     << "file:\n"
     << "   <filename>       | execute file.\n"
     << "argv:\n"
@@ -75,13 +77,18 @@ std::ostream& logo(std::ostream& out) {
     << "   /  \\/ / _` / __|/ _` | |\n"
     << "  / /\\  / (_| \\__ \\ (_| | |\n"
     << "  \\_\\ \\/ \\__,_|___/\\__,_|_|\n"
-    << "ver  : " << __nasver << " (" << __DATE__ << " " << __TIME__ << ")\n"
+    << "\n"
+    << "ver  : " << __nasver__
+    << " " << nasal::get_platform() << " " << nasal::get_arch()
+    << " (" << __DATE__ << " " << __TIME__ << ")\n"
     << "std  : c++ " << __cplusplus << "\n"
     << "core : " << std::thread::hardware_concurrency() << " core(s)\n"
     << "repo : https://github.com/ValKmjolnir/Nasal-Interpreter\n"
     << "repo : https://gitee.com/valkmjolnir/Nasal-Interpreter\n"
     << "wiki : https://wiki.flightgear.org/Nasal_scripting_language\n"
     << "\n"
+    << "presented by fgprc members - http://fgprc.org.cn\n"
+    << "\n"
     << "input <nasal -h> to get help .\n\n";
     return out;
 }
@@ -95,7 +102,8 @@ std::ostream& version(std::ostream& out) {
     if (num<0.01) {
         nasal::parse::easter_egg();
     }
-    out << "nasal interpreter version " << __nasver;
+    out << "nasal interpreter version " << __nasver__;
+    out << " " << nasal::get_platform() << " " << nasal::get_arch();
     out << " (" << __DATE__ << " " << __TIME__ << ")\n";
     return out;
 }
@@ -127,12 +135,11 @@ void execute(
     // parser gets lexer's token list to compile
     parse.compile(lex).chkerr();
     if (cmd&VM_RAW_AST) {
-        auto dumper = std::unique_ptr<nasal::ast_dumper>(new nasal::ast_dumper);
-        dumper->dump(parse.tree());
+        nasal::ast_dumper().dump(parse.tree());
     }
 
     // linker gets parser's ast and load import files to this ast
-    ld.link(parse, file, cmd&VM_DETAIL).chkerr();
+    ld.link(parse, cmd&VM_DETAIL).chkerr();
     if (cmd&VM_REF_FILE) {
         if (ld.get_file_list().size()) {
             std::cout << "referenced file(s):\n";
@@ -146,12 +153,11 @@ void execute(
     auto opt = std::unique_ptr<nasal::optimizer>(new nasal::optimizer);
     opt->do_optimization(parse.tree());
     if (cmd&VM_AST) {
-        auto dumper = std::unique_ptr<nasal::ast_dumper>(new nasal::ast_dumper);
-        dumper->dump(parse.tree());
+        nasal::ast_dumper().dump(parse.tree());
     }
 
     // code generator gets parser's ast and import file list to generate code
-    gen.compile(parse, ld, false).chkerr();
+    gen.compile(parse, ld, false, cmd&VM_LIMIT).chkerr();
     if (cmd&VM_CODE) {
         gen.print(std::cout);
     }
@@ -167,6 +173,7 @@ void execute(
     } else if (cmd&VM_TIME || cmd&VM_EXEC) {
         auto runtime = std::unique_ptr<nasal::vm>(new nasal::vm);
         runtime->set_detail_report_info(cmd&VM_DETAIL);
+        runtime->set_limit_mode_flag(cmd&VM_LIMIT);
         runtime->run(gen, ld, argv);
     }
 
@@ -223,7 +230,8 @@ i32 main(i32 argc, const char* argv[]) {
         {"--prof", VM_PROFILE},
         {"--prof-all", VM_PROF_ALL},
         {"-f", VM_REF_FILE},
-        {"--ref-file", VM_REF_FILE}
+        {"--ref-file", VM_REF_FILE},
+        {"--limit", VM_LIMIT|VM_EXEC}
     };
     u32 cmd = 0;
     std::string filename = "";
diff --git a/src/nasal.h b/src/nasal.h
index ccfd9b7..e458572 100644
--- a/src/nasal.h
+++ b/src/nasal.h
@@ -1,7 +1,7 @@
 #pragma once
 
-#ifndef __nasver
-#define __nasver "11.1"
+#ifndef __nasver__
+#define __nasver__ "11.1"
 #endif
 
 #include <cstdint>
@@ -34,7 +34,8 @@ bool is_aarch64();
 bool is_ia64();
 bool is_powerpc();
 bool is_superh();
-
+const char* get_platform();
+const char* get_arch();
 
 // virtual machine stack depth, both global depth and value stack depth
 const u32 STACK_DEPTH = 4096;
diff --git a/src/nasal_builtin.cpp b/src/nasal_builtin.cpp
index e3bc834..58aee78 100644
--- a/src/nasal_builtin.cpp
+++ b/src/nasal_builtin.cpp
@@ -3,6 +3,13 @@
 
 namespace nasal {
 
+var builtin_unsafe(context* ctx, gc* ngc) {
+    return nas_err(
+        "unsafe_redirect",
+        "you are using unsafe system api under limited mode!"
+    );
+}
+
 var builtin_print(context* ctx, gc* ngc) {
     for(auto& i : ctx->localr[1].vec().elems) {
         std::cout << i;
@@ -447,35 +454,11 @@ var builtin_sleep(context* ctx, gc* ngc) {
 }
 
 var builtin_platform(context* ctx, gc* ngc) {
-    if (is_windows()) {
-        return ngc->newstr("windows");
-    } else if (is_linux()) {
-        return ngc->newstr("linux");
-    } else if (is_macos()) {
-        return ngc->newstr("macOS");
-    }
-    return ngc->newstr("unknown");
+    return ngc->newstr(get_platform());
 }
 
 var builtin_arch(context* ctx, gc* ngc) {
-    if (is_x86()) {
-        return ngc->newstr("x86");
-    } else if (is_x86_64()) {
-        return ngc->newstr("x86-64");
-    } else if (is_amd64()) {
-        return ngc->newstr("amd64");
-    } else if (is_arm()) {
-        return ngc->newstr("arm");
-    } else if (is_aarch64()) {
-        return ngc->newstr("aarch64");
-    } else if (is_ia64()) {
-        return ngc->newstr("ia64");
-    } else if (is_powerpc()) {
-        return ngc->newstr("powerpc");
-    } else if (is_superh()) {
-        return ngc->newstr("superh");
-    }
-    return ngc->newstr("unknown");
+    return ngc->newstr(get_arch());
 }
 
 // md5 related functions
@@ -683,7 +666,7 @@ var builtin_logtime(context* ctx, gc* ngc) {
     tm* tm_t = localtime(&t);
     char s[64];
     snprintf(
-        s,64,"%d-%.2d-%.2d %.2d:%.2d:%.2d",
+        s, 64, "%d-%.2d-%.2d %.2d:%.2d:%.2d",
         tm_t->tm_year+1900,
         tm_t->tm_mon+1,
         tm_t->tm_mday,
diff --git a/src/nasal_builtin.h b/src/nasal_builtin.h
index d366879..9ca7503 100644
--- a/src/nasal_builtin.h
+++ b/src/nasal_builtin.h
@@ -29,6 +29,7 @@
 
 namespace nasal {
 
+var builtin_unsafe(context*, gc*);
 var builtin_print(context*, gc*);
 var builtin_println(context*, gc*);
 var builtin_exit(context*, gc*);
diff --git a/src/nasal_codegen.cpp b/src/nasal_codegen.cpp
index 95a135e..c6328a0 100644
--- a/src/nasal_codegen.cpp
+++ b/src/nasal_codegen.cpp
@@ -11,12 +11,18 @@ void codegen::init_file_map(const std::vector<std::string>& file_list) {
 
 void codegen::load_native_function_table(nasal_builtin_table* table) {
     for(usize i = 0; table[i].func; ++i) {
+        // check confliction
         if (native_function_mapper.count(table[i].name)) {
             err.err("code", "\"" + std::string(table[i].name) + "\" conflicts.");
             continue;
         }
-        native_function.push_back(table[i]);
+        if (flag_limited_mode && unsafe_system_api.count(table[i].name)) {
+            native_function.push_back({"__unsafe_redirect", builtin_unsafe});
+        } else {
+            native_function.push_back(table[i]);
+        }
         auto index = native_function_mapper.size();
+        // insert into mapper
         native_function_mapper[table[i].name] = index;
     }
 }
@@ -1302,10 +1308,14 @@ void codegen::ret_gen(return_expr* node) {
     emit(op_ret, 0, node->get_location());
 }
 
-const error& codegen::compile(parse& parse, linker& import, bool repl_flag) {
+const error& codegen::compile(parse& parse,
+                              linker& import,
+                              bool repl_flag,
+                              bool limit_mode) {
+    need_repl_output = repl_flag;
+    flag_limited_mode = limit_mode;
     init_native_function();
     init_file_map(import.get_file_list());
-    need_repl_output = repl_flag;
 
     in_foreach_loop_level.push_back(0);
 
diff --git a/src/nasal_codegen.h b/src/nasal_codegen.h
index 221a0d3..9d8ec7f 100644
--- a/src/nasal_codegen.h
+++ b/src/nasal_codegen.h
@@ -37,6 +37,24 @@ private:
 
     // repl output flag, will generate op_repl to output stack top value if true
     bool need_repl_output;
+    // limit mode flag
+    bool flag_limited_mode;
+    const std::unordered_set<std::string> unsafe_system_api = {
+        // builtin
+        "__system", "__input",
+        // io
+        "__fout", "__open", "__write", "__stat"
+        // bits
+        "__fld", "__sfld", "__setfld",
+        "__buf",
+        // fg
+        "__logprint",
+        // dylib
+        "__dlopen", "__dlclose", "__dlcallv", "__dlcall",
+        // unix
+        "__pipe", "__fork", "__waitpid", "__chdir",
+        "__environ", "__getcwd", "__getenv"
+    };
 
     // file mapper for file -> index
     std::unordered_map<std::string, usize> file_map;
@@ -141,7 +159,7 @@ public:
 
 public:
     codegen() = default;
-    const error& compile(parse&, linker&, bool);
+    const error& compile(parse&, linker&, bool, bool);
     void print(std::ostream&);
     void symbol_dump(std::ostream&) const;
 };
diff --git a/src/nasal_err.h b/src/nasal_err.h
index bbeeb2a..3aec9bf 100644
--- a/src/nasal_err.h
+++ b/src/nasal_err.h
@@ -31,7 +31,7 @@ protected:
     std::vector<std::string> res;
 
 public:
-    flstream():file("") {}
+    flstream(): file("") {}
     void load(const std::string&);
     const std::string& operator[](usize n) const {return res[n];}
     const auto& name() const {return file;}
@@ -39,23 +39,23 @@ public:
     usize size() const {return res.size();}
 };
 
-class error:public flstream {
+class error: public flstream {
 private:
     u32 cnt; // counter for errors
 
     std::string identation(usize len) {
-        return std::string(len,' ');
+        return std::string(len, ' ');
     }
     std::string leftpad(u32 num, usize len) {
         auto tmp = std::to_string(num);
         while(tmp.length()<len) {
-            tmp=" "+tmp;
+            tmp = " "+tmp;
         }
         return tmp;
     }
 
 public:
-    error():cnt(0) {}
+    error(): cnt(0) {}
     void err(const std::string&, const std::string&);
     void warn(const std::string&, const std::string&);
     void err(const std::string&, const span&, const std::string&);
diff --git a/src/nasal_import.cpp b/src/nasal_import.cpp
index 0d06ea7..123f956 100644
--- a/src/nasal_import.cpp
+++ b/src/nasal_import.cpp
@@ -6,7 +6,7 @@
 
 namespace nasal {
 
-linker::linker(): show_path_flag(false), library_loaded(false), this_file("") {
+linker::linker(): show_path_flag(false), this_file("") {
     const auto seperator = is_windows()? ';':':';
     const auto PATH = std::string(getenv("PATH"));
     usize last = 0, position = PATH.find(seperator, 0);
@@ -155,7 +155,7 @@ std::string linker::generate_self_import_path(const std::string& filename) {
     return res + "[" + filename + "]";
 }
 
-void linker::link(code_block* new_tree_root, code_block* old_tree_root) {
+void linker::merge_tree(code_block* new_tree_root, code_block* old_tree_root) {
     // add children of add_root to the back of root
     for(auto& i : old_tree_root->get_expressions()) {
         new_tree_root->add_expression(i);
@@ -179,32 +179,48 @@ code_block* linker::import_regular_file(
     // check self import, avoid infinite loading loop
     if (check_self_import(filename)) {
         err.err("link",
-            "self-referenced module <" + filename + ">:\n" +
-            "    reference path: " + generate_self_import_path(filename)
+            node->get_location(),
+            "self-referenced module <" + filename + ">, " +
+            "reference path: " + generate_self_import_path(filename)
         );
         return new code_block({0, 0, 0, 0, filename});
     }
     check_exist_or_record_file(filename);
-    
+
     module_load_stack.push_back(filename);
+    // avoid stack overflow
+    if (module_load_stack.size()>MAX_RECURSION_DEPTH) {
+        err.err("link",
+            node->get_location(),
+            "too deep module import stack (>" +
+            std::to_string(MAX_RECURSION_DEPTH) + ")."
+        );
+        return new code_block({0, 0, 0, 0, filename});
+    }
     // start importing...
     lexer nasal_lexer;
     parse nasal_parser;
     if (nasal_lexer.scan(filename).geterr()) {
-        err.err("link", "error occurred when analysing <" + filename + ">");
+        err.err("link",
+            node->get_location(),
+            "error occurred when analysing <" + filename + ">"
+        );
         return new code_block({0, 0, 0, 0, filename});
     }
     if (nasal_parser.compile(nasal_lexer).geterr())  {
-        err.err("link", "error occurred when analysing <" + filename + ">");
+        err.err("link",
+            node->get_location(),
+            "error occurred when analysing <" + filename + ">"
+        );
         return new code_block({0, 0, 0, 0, filename});
     }
     // swap result out
     auto parse_result = nasal_parser.swap(nullptr);
 
     // check if parse result has 'import'
-    auto result = load(parse_result, filename);
+    load(parse_result, filename);
     module_load_stack.pop_back();
-    return result;
+    return parse_result;
 }
 
 code_block* linker::import_nasal_lib() {
@@ -238,10 +254,12 @@ code_block* linker::import_nasal_lib() {
     // swap result out
     auto parse_result = nasal_parser.swap(nullptr);
     // check if library has 'import' (in fact it should not)
-    return load(parse_result, path);
+    load(parse_result, path);
+    return parse_result;
 }
 
 std::string linker::generate_module_name(const std::string& file_path) {
+    // import("...") may trigger this error module name
     auto error_name = "module@[" + file_path + "]";
     if (!file_path.length()) {
         return error_name;
@@ -316,13 +334,19 @@ return_expr* linker::generate_module_return(code_block* block) {
 }
 
 definition_expr* linker::generate_module_definition(code_block* block) {
+    // generate ast node like this:
+    // var {module_name} = (func() {
+    //     ... # module itself
+    // })();
     auto def = new definition_expr(block->get_location());
     def->set_identifier(new identifier(
         block->get_location(),
         generate_module_name(block->get_location().file)
     ));
     
+    // (func() {...})();
     auto call = new call_expr(block->get_location());
+    // func() {...}
     auto func = new function(block->get_location());
     func->set_code_block(block);
     func->get_code_block()->add_expression(generate_module_return(block));
@@ -333,18 +357,7 @@ definition_expr* linker::generate_module_definition(code_block* block) {
     return def;
 }
 
-code_block* linker::load(code_block* program_root, const std::string& filename) {
-    auto tree = new code_block({0, 0, 0, 0, filename});
-    // load library, this ast will be linked with root directly
-    // so no extra namespace is generated
-    if (!library_loaded) {
-        auto nasal_lib_code_block = import_nasal_lib();
-        // insert nasal lib code to the back of tree
-        link(tree, nasal_lib_code_block);
-        delete nasal_lib_code_block;
-        library_loaded = true;
-    }
-
+void linker::load(code_block* program_root, const std::string& filename) {
     // load imported modules
     std::unordered_set<std::string> used_modules = {};
     for(auto& import_node : program_root->get_expressions()) {
@@ -353,46 +366,46 @@ code_block* linker::load(code_block* program_root, const std::string& filename)
         }
         // parse file and get ast
         auto module_code_block = import_regular_file(import_node, used_modules);
-        auto replace_node = new null_expr(import_node->get_location());
-        // after importing the regular file as module, delete this node
-        delete import_node;
-        // and replace the node with null_expr node
-        import_node = replace_node;
 
-        // avoid repeatedly importing the same module
+        // avoid repeatedly importing the same module in one file
         const auto& module_path = module_code_block->get_location().file;
         if (used_modules.count(module_path)) {
             delete module_code_block;
+            auto replace_node = new null_expr(import_node->get_location());
+            // after importing the regular file as module, delete this node
+            delete import_node;
+            // and replace the node with null_expr node
+            import_node = replace_node;
             continue;
         }
-        
+        used_modules.insert(module_path);
+        delete import_node;
         // then we generate a function warping the code block,
         // and export the necessary global symbols in this code block
         // by generate a return statement, with a hashmap return value
-        used_modules.insert(module_path);
-        tree->add_expression(generate_module_definition(module_code_block));
+        import_node = generate_module_definition(module_code_block);
     }
-
-    // insert program root to the back of tree
-    link(tree, program_root);
-    return tree;
 }
 
-const error& linker::link(
-    parse& parse, const std::string& self, bool spath = false) {
+const error& linker::link(parse& parse, bool spath = false) {
     // switch for showing path when errors occur
     show_path_flag = spath;
 
     // initializing file map
-    this_file = self;
-    imported_files = {self};
-    module_load_stack = {self};
+    this_file = parse.tree()->get_location().file;
+    imported_files = {this_file};
+    module_load_stack = {this_file};
 
     // scan root and import files
     // then generate a new ast and return to import_ast
-    auto new_tree_root = load(parse.tree(), self);
-    auto old_tree_root = parse.swap(new_tree_root);
-    delete old_tree_root;
+    // dfs load file
+    auto library = import_nasal_lib();
+    // load used modules of this file
+    load(parse.tree(), this_file);
+    // then insert the whole tree into library tree root
+    merge_tree(library, parse.tree());
+    // swap tree root, and delete old root
+    delete parse.swap(library);
     return err;
 }
 
diff --git a/src/nasal_import.h b/src/nasal_import.h
index 692c922..420d6d6 100644
--- a/src/nasal_import.h
+++ b/src/nasal_import.h
@@ -23,8 +23,8 @@ namespace nasal {
 
 class linker {
 private:
+    const u32 MAX_RECURSION_DEPTH = 256;
     bool show_path_flag;
-    bool library_loaded;
     std::string this_file;
     error err;
     std::vector<std::string> imported_files;
@@ -36,7 +36,7 @@ private:
     bool check_exist_or_record_file(const std::string&);
     bool check_self_import(const std::string&);
     std::string generate_self_import_path(const std::string&);
-    void link(code_block*, code_block*);
+    void merge_tree(code_block*, code_block*);
     std::string get_path(expr*);
     std::string find_real_file_path(const std::string&, const span&);
     code_block* import_regular_file(expr*, std::unordered_set<std::string>&);
@@ -44,11 +44,11 @@ private:
     std::string generate_module_name(const std::string&);
     return_expr* generate_module_return(code_block*);
     definition_expr* generate_module_definition(code_block*);
-    code_block* load(code_block*, const std::string&);
+    void load(code_block*, const std::string&);
 
 public:
     linker();
-    const error& link(parse&, const std::string&, bool);
+    const error& link(parse&, bool);
     const auto& get_file_list() const {return imported_files;}
 };
 
diff --git a/src/nasal_misc.cpp b/src/nasal_misc.cpp
index 11f8297..13f7f30 100644
--- a/src/nasal_misc.cpp
+++ b/src/nasal_misc.cpp
@@ -97,6 +97,38 @@ bool is_superh() {
 #endif
 }
 
+const char* get_platform() {
+    if (is_windows()) {
+        return "windows";
+    } else if (is_linux()) {
+        return "linux";
+    } else if (is_macos()) {
+        return "macOS";
+    }
+    return "unknown platform";
+}
+
+const char* get_arch() {
+    if (is_x86()) {
+        return "x86";
+    } else if (is_x86_64()) {
+        return "x86-64";
+    } else if (is_amd64()) {
+        return "amd64";
+    } else if (is_arm()) {
+        return "arm";
+    } else if (is_aarch64()) {
+        return "aarch64";
+    } else if (is_ia64()) {
+        return "ia64";
+    } else if (is_powerpc()) {
+        return "powerpc";
+    } else if (is_superh()) {
+        return "superh";
+    }
+    return "unknown arch";
+}
+
 f64 hex_to_f64(const char* str) {
     f64 ret = 0;
     for(; *str; ++str) {
diff --git a/src/nasal_vm.h b/src/nasal_vm.h
index 8653818..8da79d6 100644
--- a/src/nasal_vm.h
+++ b/src/nasal_vm.h
@@ -45,6 +45,9 @@ protected:
     bool first_exec_flag = true;
     bool allow_repl_output = false;
 
+    /* limited mode, will not load unsafe system api if switch on */
+    bool flag_limited_mode = false;
+
     /* vm initializing function */
     void init(
         const std::vector<std::string>&,
@@ -192,6 +195,8 @@ public:
     void set_repl_mode_flag(bool flag) {is_repl_mode = flag;}
     /* set repl output flag */
     void set_allow_repl_output_flag(bool flag) {allow_repl_output = flag;}
+    /* set limit mode flag */
+    void set_limit_mode_flag(bool flag) {flag_limited_mode = flag;}
 };
 
 inline bool vm::cond(var& val) {
diff --git a/src/repl.cpp b/src/repl.cpp
index 2773700..10860b3 100644
--- a/src/repl.cpp
+++ b/src/repl.cpp
@@ -92,12 +92,12 @@ bool repl::run() {
         return false;
     }
 
-    if (nasal_linker->link(*nasal_parser, "<nasal-repl>", true).geterr()) {
+    if (nasal_linker->link(*nasal_parser, true).geterr()) {
         return false;
     }
 
     nasal_opt->do_optimization(nasal_parser->tree());
-    if (nasal_codegen->compile(*nasal_parser, *nasal_linker, true).geterr()) {
+    if (nasal_codegen->compile(*nasal_parser, *nasal_linker, true, false).geterr()) {
         return false;
     }
 
@@ -120,7 +120,7 @@ void repl::execute() {
     std::cout << "[nasal-repl] Initialization complete.\n\n";
 
     // finish initialization, output version info
-    std::cout << "Nasal REPL interpreter version " << __nasver;
+    std::cout << "Nasal REPL interpreter version " << __nasver__;
     std::cout << " (" << __DATE__ << " " << __TIME__ << ")\n";
     help();
 
diff --git a/test/langtons-ant.nas b/test/langtons-ant.nas
new file mode 100644
index 0000000..9eed9a9
--- /dev/null
+++ b/test/langtons-ant.nas
@@ -0,0 +1,97 @@
+use std.unix;
+
+srand();
+
+var ant = {
+    new: func(color, pos_x, pos_y) {
+        return {
+            move: int(rand()*4),
+            color: color,
+            pos_x: pos_x,
+            pos_y: pos_y
+        };
+    }
+};
+
+# generate agents
+var ants = [
+    ant.new(10, 30, 15),
+    ant.new(11, 31, 16),
+    ant.new(4, 29, 13),
+    ant.new(9, 30, 14),
+    ant.new(13, 30, 12),
+    ant.new(99, 25, 18)
+];
+
+# initialize game map
+var map = [];
+var map_color = [];
+setsize(map, 60*30);
+setsize(map_color, 60*30);
+forindex(var i; map) {
+    map[i] = 0;
+    map_color[i] = 0;
+}
+foreach(var a; ants) {
+    map_color[a.pos_x + a.pos_y*60] = a.color;
+}
+
+var print_map = func {
+    var res = "\e[1;1H";
+    for(var y = 0; y<30; y += 1) {
+        for(var x = 0; x<60; x += 1) {
+            res ~= "\e[38;5;"~map_color[x + y*60]~";1m";
+            res ~= map[x + y*60] ~ " \e[0m";
+        }
+        res ~= "\n";
+    }
+    print(res);
+}
+
+var move = func {
+    var move_step = [
+        [0, -1],
+        [1, 0],
+        [0, 1],
+        [-1, 0]
+    ];
+    var temp_map = [];
+    setsize(temp_map, 60*30);
+    forindex(var i; map) {
+        temp_map[i] = map[i];
+    }
+    foreach(var a; ants) {
+        var map_state = map[a.pos_x + a.pos_y*60];
+        temp_map[a.pos_x + a.pos_y*60] = map_state==0? 1:0;
+        if (map_state==1) {
+            a.move -= 1;
+            if (a.move < 0) {
+                a.move = 3;
+            }
+        } else {
+            a.move += 1;
+            if (a.move > 3) {
+                a.move = 0;
+            }
+        }
+        a.pos_x += move_step[a.move][0];
+        a.pos_y += move_step[a.move][1];
+        if (a.pos_x < 0) { a.pos_x = 59; }
+        if (a.pos_x > 59) { a.pos_x = 0; }
+        if (a.pos_y < 0) { a.pos_y = 29; }
+        if (a.pos_y > 29) { a.pos_y = 0; }
+
+        if (map_color[a.pos_x + a.pos_y*60]!=a.color) {
+            map_color[a.pos_x + a.pos_y*60] = a.color;
+        } else {
+            map_color[a.pos_x + a.pos_y*60] = 0;
+        }
+    }
+    map = temp_map;
+}
+
+while(1) {
+    print_map();
+    move();
+    unix.sleep(1/24);
+}
\ No newline at end of file