diff --git a/home.nix b/home.nix
index 33bc21c4..28143d84 100644
--- a/home.nix
+++ b/home.nix
@@ -10,17 +10,13 @@
 #MC 我利用环境变量`DISPLAY`用于判断是否导入GUI程序的配置。
 
 { config, pkgs, stdenv, lib, ... }:
-
-{
+let
+  opt = import ./opt.nix;
+in {
   imports = [
-    ./opt.nix
     ./usr/modules/cachix.nix
     ./usr/cli.nix
-    # Q: how to use isGui here?
-    # A: Not possible.
-    #    As isGui is evaluated after `imports` being evaluated,
-    #    use config.isGui here cause infinite loop.
-  ] ++ lib.optionals ((builtins.getEnv "DISPLAY")!="") [
+  ] ++ lib.optionals opt.isGui [
     ./usr/gui.nix
   ];
 
diff --git a/opt.nix b/opt.nix
index d434da09..25c75951 100644
--- a/opt.nix
+++ b/opt.nix
@@ -2,46 +2,49 @@
 #MC
 #MC nix语言中只有`let ... in`来定义局部变量，没有提供全局变量的语法支持。
 #MC 但在我的nix配置中又很需要一些“全局变量”来方便统一的管理多个配置文件。
+#MC 有2种可行的方案来实现全局变量：module和import。
+#MC
+#MC ## module
+#MC
 #MC nixpkgs的module能够还不错地实现“全局变量”。
-#MC 我的`opt.nix`即利用module的options定了多个可以供其他modules使用的全局变量。
 #MC 想了解module？可以去看看[NixOS wikiL modules](https://nixos.wiki/wiki/NixOS_modules)。
 #MC 或者看看nixpkgs源码关于modules.nix的部分`<nixpkgs>/lib/modules.nix`。
 #MC
 #MC 要注意的是，基于module的“全局变量”也会有<span style="color:red;">**局限**</span>的。
 #MC module是用过imports变量导入的，若在imports语句访问“全局变量”，nix的lazy evaluation的特性会导致死循环。
-#MC 这也是为什么[home.nix](./home.nix.md)中判断是否需要导入[./usr/gui.nix](./usr/gui.nix.md)，
+#MC 这也是为什么老版本的[home.nix](./home.nix.md)中判断是否需要导入[./usr/gui.nix](./usr/gui.nix.md)，
 #MC 我没有使用`config.isGui`而是再次使用getEnv访问环境变量。
+#MC 当然这个不足也是我放弃使用的module主要原因。
+#MC
+#MC ## import
 #MC
-#MC 下面是我的配置的全局变量及注解。
-
-{ config, pkgs, stdenv, lib, ... }:
-
-{ options = {
+#MC 通过在配置文件中import opt.nix也能还不错的实现“全局变量”。
+#MC import方法的最大优势是能够在module imports语句中避免死循环。
+#MC
+#MC 这个方法的不足之处在于每个需要使用全局变量的文件都需要import opt.nix。
+#MC 但这个不方便之处，相对imports死循环，没那么让人难受。
+{
+  isMinimalConfig = false;
   #MC `proxyPort`：代理端口号，诸多网络程序需要用，比如clash和tailscale。
-  proxyPort = lib.mkOption {
-    default = 8889;
-    readOnly = true;
-  };
+  proxyPort = 8889;
   #MC `isCli`和`isGui`：通过环境变量`DISPLAY`来判断是否是CLI或GUI环境。
   #MC 这个方法有<span style="color:red;">**局限**</span>，比如ssh连接到一台有GUI的电脑上，ssh里是没有设置环境变量`DISPLAY`的。
-  #MC 若直接执行`home-manager switch`，则这台电脑上的GUI程序都会被禁用。
-  #MC 缓解的方法也很简单，手动写个环境变量就好，比如`DISPLAY=1 home-manager switch`就OK啦😺。
-  isCli = lib.mkOption {
-    default = (builtins.getEnv "DISPLAY")=="";
-    readOnly = true;
-  };
-  isGui = lib.mkOption {
-    default = (builtins.getEnv "DISPLAY")!="";
-    readOnly = true;
-  };
+  #MC 因此更好的方法是在opt-local.nix中写入固定的isCli和isGui值。
+  isCli = (builtins.getEnv "DISPLAY")=="";
+  isGui = (builtins.getEnv "DISPLAY")!="";
   #MC `isNixOnDroid`：通过用户名来判断是否是nix-on-droid。
-  isNixOnDroid = lib.mkOption {
-    default = config.home.username == "nix-on-droid";
-    readOnly = true;
-  };
+  isNixOnDroid = (builtins.getEnv "USER")=="nix-on-droid";
   #MC `isWSL2`：通过环境变量`WSL_DISTRO_NAME`来判断是否是WSL2。
-  isWSL2 = lib.mkOption {
-    default = (builtins.getEnv "WSL_DISTRO_NAME")!="";
-    readOnly = true;
-  };
-};}
+  isWSL2 = (builtins.getEnv "WSL_DISTRO_NAME")!="";
+}
+#MC ### 本地配置
+#MC
+#MC 引入opt-local.nix，方便本地进行自定义，避免我的nix配置中出现过多设备特定代码（即一堆if else判断语句）。
+#MC 为了减少设备特定代码，每个设备都有自己的opt-local.nix。
+#MC 目前的想法是不将opt-local.nix加入git仓库，以实现“设备特定”。
+#MC 相比opt.nix，opt-local.nix的配置具备更高的优先级。
+// (
+  if (builtins.pathExists ./opt4-local.nix)
+  then import ./opt4-local.nix
+  else {}
+)
diff --git a/opt4imports.nix b/opt4imports.nix
deleted file mode 100644
index 4c122b1b..00000000
--- a/opt4imports.nix
+++ /dev/null
@@ -1,7 +0,0 @@
-{
-  isMinimalConfig = false;
-} // (
-  if (builtins.pathExists ./opt4imports-local.nix)
-  then import ./opt4imports-local.nix
-  else {}
-)
diff --git a/usr/cli-extra.nix b/usr/cli-extra.nix
index 72902f87..6196245f 100644
--- a/usr/cli-extra.nix
+++ b/usr/cli-extra.nix
@@ -1,6 +1,8 @@
 #MC # cli-extra.nix: Extra CLI configs (added to minial cli.nix)
 { config, pkgs, stdenv, lib, ... }:
-{
+let
+  opt = import ../opt.nix;
+in {
   imports = [{
     home.packages = let
       pandora = pkgs.python3Packages.callPackage ./cli/pandora-chatgpt.nix {};
@@ -21,12 +23,12 @@
 
           # use host proxy
           "--container-options" "--network=host"
-          "--env" "HTTPS_PROXY='http://127.0.0.1:${toString config.proxyPort}'"
-          "--env" "HTTP_PROXY='http://127.0.0.1:${toString config.proxyPort}'"
-          "--env" "FTP_PROXY='http://127.0.0.1:${toString config.proxyPort}'"
-          "--env" "https_proxy='http://127.0.0.1:${toString config.proxyPort}'"
-          "--env" "http_proxy='http://127.0.0.1:${toString config.proxyPort}'"
-          "--env" "ftp_proxy='http://127.0.0.1:${toString config.proxyPort}'"
+          "--env" "HTTPS_PROXY='http://127.0.0.1:${toString opt.proxyPort}'"
+          "--env" "HTTP_PROXY='http://127.0.0.1:${toString opt.proxyPort}'"
+          "--env" "FTP_PROXY='http://127.0.0.1:${toString opt.proxyPort}'"
+          "--env" "https_proxy='http://127.0.0.1:${toString opt.proxyPort}'"
+          "--env" "http_proxy='http://127.0.0.1:${toString opt.proxyPort}'"
+          "--env" "ftp_proxy='http://127.0.0.1:${toString opt.proxyPort}'"
 
           "$@"
         )
diff --git a/usr/cli.nix b/usr/cli.nix
index 2e6bf1f5..3cba2c8b 100644
--- a/usr/cli.nix
+++ b/usr/cli.nix
@@ -1,6 +1,6 @@
 { config, pkgs, stdenv, lib, ... }:
 let
-  opt4imports = import ../opt4imports.nix;
+  opt = import ../opt.nix;
   git-wip = builtins.derivation {
     name = "git-wip";
     system = builtins.currentSystem;
@@ -75,12 +75,13 @@ let
   ).config;
 in
 {
-  imports = lib.optionals (!opt4imports.isMinimalConfig) [
+  imports = lib.optionals (!opt.isMinimalConfig) [
     ./cli-extra.nix
   ] ++ [ # files
     ./cli/vim
     ./cli/clash.nix
     ./cli/tailscale.nix
+    ./cli/zsh.nix
     # When init searxng, it throws `ERROR:searx.engines.wikidata: Fail to initialize`
     # I have no idea, so disable it.
     # ./cli/searxng.nix
@@ -94,8 +95,8 @@ in
       export FZF_DEFAULT_OPTS="--reverse"
     '';
   }{
-    home.packages = lib.optional (!config.isNixOnDroid) pkgs.hstr;
-    programs.bash.bashrcExtra = lib.optionalString (!config.isNixOnDroid) ''
+    home.packages = lib.optional (!opt.isNixOnDroid) pkgs.hstr;
+    programs.bash.bashrcExtra = lib.optionalString (!opt.isNixOnDroid) ''
       # HSTR configuration - add this to ~/.bashrc
       alias hh=hstr                    # hh to be alias for hstr
       export HSTR_CONFIG=hicolor       # get more colors
@@ -111,7 +112,7 @@ in
   }{
     programs.ssh.enable = true;
     programs.ssh.includes = lib.optional (builtins.pathExists ~/Gist/Config/ssh.conf) "~/Gist/Config/ssh.conf";
-    programs.bash.bashrcExtra = lib.optionalString config.isNixOnDroid ''
+    programs.bash.bashrcExtra = lib.optionalString opt.isNixOnDroid ''
       # start sshd
       if [[ -z "$(pidof sshd-start)" ]]; then
           tmux new -d -s sshd-start sshd-start
@@ -226,15 +227,15 @@ in
     services.syncthing = {
       enable = true;
       #MC 让syncthing的端口外部可访问。
-      extraOptions = lib.optional config.isCli "--gui-address=0.0.0.0:8384";
+      extraOptions = lib.optional opt.isCli "--gui-address=0.0.0.0:8384";
     };
     #MC 启用代理，因为有些syncthing的服务器似乎是被墙了的。
     systemd.user.services.syncthing.Service.Environment = [
       # https://docs.syncthing.net/users/proxying.html
-      "http_proxy=http://127.0.0.1:${toString config.proxyPort}"
+      "http_proxy=http://127.0.0.1:${toString opt.proxyPort}"
     ];
     #MC 使用命令行浏览器browsh来实现syncthing-tui。
-    home.packages = lib.optional (!opt4imports.isMinimalConfig) (
+    home.packages = lib.optional (!opt.isMinimalConfig) (
       pkgs.writeShellScriptBin "syncthing-tui" ''
         ${pkgs.browsh}/bin/browsh --firefox.path ${pkgs.firefox}/bin/firefox http://127.0.0.1:8384
       ''
@@ -353,7 +354,7 @@ in
     if [[ -n "$IN_NIX_SHELL" ]]; then
         PS1+="(''${name}.$IN_NIX_SHELL)"
     fi
-    PS1+="''${u_green}\u${lib.optionalString (!config.isNixOnDroid) "@\\h"}''${u_white}:"
+    PS1+="''${u_green}\u${lib.optionalString (!opt.isNixOnDroid) "@\\h"}''${u_white}:"
     PS1+="''${u_blue}\w''${u_white}"
     PS1+="\n''${u_green}\$''${u_white} "
     unset u_green u_blue u_white
@@ -390,7 +391,7 @@ in
     if [[ -n $(command -v eza) ]]; then
         alias ls=eza
     fi
-  '' + lib.optionalString config.isWSL2 ''
+  '' + lib.optionalString opt.isWSL2 ''
     # use the working directory of the current tab as the starting directory for a new tab
     # https://learn.microsoft.com/en-us/windows/terminal/tutorials/new-tab-same-directory#using-actions-to-duplicate-the-path
     PROMPT_COMMAND=''${PROMPT_COMMAND:+"$PROMPT_COMMAND"}'printf "\e]9;9;%s\e\\" "$(wslpath -w "$PWD")"'
diff --git a/usr/cli/clash.nix b/usr/cli/clash.nix
index 9a5c0b73..396b12ef 100644
--- a/usr/cli/clash.nix
+++ b/usr/cli/clash.nix
@@ -1,12 +1,13 @@
 { config, pkgs, stdenv, lib, ... }:
 let
+  opt = import ../../opt.nix;
   clashctl = pkgs.callPackage ./clashctl.nix {};
 in {
   imports = [{
     home.packages = [
       pkgs.clash-meta
-    ] ++ lib.optional (!config.isNixOnDroid) clashctl;
-    cachix_packages = lib.optional (!config.isNixOnDroid) clashctl;
+    ] ++ lib.optional (!opt.isNixOnDroid) clashctl;
+    cachix_packages = lib.optional (!opt.isNixOnDroid) clashctl;
 
     systemd.user.services.clash = {
       Unit = {
@@ -20,14 +21,14 @@ in {
         ExecStart = "${pkgs.clash-meta.outPath}/bin/clash-meta -d ${config.home.homeDirectory}/Gist/clash";
       };
     };
-    programs.bash.bashrcExtra = lib.mkBefore (lib.optionalString (!config.isNixOnDroid) ''
+    programs.bash.bashrcExtra = lib.mkBefore (lib.optionalString (!opt.isNixOnDroid) ''
       # proxy
       ## default
-      HTTP_PROXY="http://127.0.0.1:${toString config.proxyPort}/"
+      HTTP_PROXY="http://127.0.0.1:${toString opt.proxyPort}/"
       ## microsoft wsl
       # if [[ $(uname -r) == *"microsoft"* ]]; then
       #     hostip=$(cat /etc/resolv.conf | grep nameserver | awk '{ print $2 }')
-      #     export HTTP_PROXY="http://$hostip:${toString config.proxyPort}"
+      #     export HTTP_PROXY="http://$hostip:${toString opt.proxyPort}"
       # fi
       export HTTPS_PROXY="$HTTP_PROXY"
       export HTTP_PROXY="$HTTP_PROXY"
diff --git a/usr/cli/searxng.nix b/usr/cli/searxng.nix
index 71791541..3b25ed0b 100644
--- a/usr/cli/searxng.nix
+++ b/usr/cli/searxng.nix
@@ -1,5 +1,6 @@
 { config, pkgs, stdenv, lib, ... }:
 let
+  opt = import ../../opt.nix;
   searxng_yml = builtins.toFile "searxng.yml" ''
     # https://docs.searxng.org/admin/settings/settings.html#settings-yml-location
     # The initial settings.yml we be load from these locations:
@@ -22,7 +23,7 @@ let
     outgoing:
       proxies:
         all://:
-          - http://127.0.0.1:${toString config.proxyPort}
+          - http://127.0.0.1:${toString opt.proxyPort}
 
     engines:
       - name: bilibili
diff --git a/usr/cli/tailscale.nix b/usr/cli/tailscale.nix
index c6dd4c0c..cce87f13 100644
--- a/usr/cli/tailscale.nix
+++ b/usr/cli/tailscale.nix
@@ -1,5 +1,6 @@
 { config, pkgs, stdenv, lib, ... }:
 let
+  opt = import ../../opt.nix;
   tailscale-bash-completion = builtins.derivation {
     name = "tailscale-bash-completion";
     system = builtins.currentSystem;
@@ -58,15 +59,15 @@ let
       };
       Service = {
         Environment = [
-          "HTTPS_PROXY=http://127.0.0.1:${toString config.proxyPort}"
-          "HTTP_PROXY=http://127.0.0.1:${toString config.proxyPort}"
-          "https_proxy=http://127.0.0.1:${toString config.proxyPort}"
-          "http_proxy=http://127.0.0.1:${toString config.proxyPort}"
+          "HTTPS_PROXY=http://127.0.0.1:${toString opt.proxyPort}"
+          "HTTP_PROXY=http://127.0.0.1:${toString opt.proxyPort}"
+          "https_proxy=http://127.0.0.1:${toString opt.proxyPort}"
+          "http_proxy=http://127.0.0.1:${toString opt.proxyPort}"
         ];
         ExecStart = "${tailscaled-wrapped}/bin/tailscaled-${suffix}";
       };
     };
-    programs.bash.bashrcExtra = lib.optionalString config.isNixOnDroid ''
+    programs.bash.bashrcExtra = lib.optionalString opt.isNixOnDroid ''
       # start tailscale-${suffix}
       if [[ -z "$(pidof tailscaled-${suffix})" ]]; then
           tmux new -d -s tailscaled-${suffix} tailscaled-${suffix}
diff --git a/usr/cli/vim/default.nix b/usr/cli/vim/default.nix
index bb910d8e..deda9986 100644
--- a/usr/cli/vim/default.nix
+++ b/usr/cli/vim/default.nix
@@ -1,5 +1,7 @@
 { config, pkgs, stdenv, lib, ... }:
-{
+let
+  opt = import ../../../opt.nix;
+in {
   #MC Plugins with customizations:
   imports = [
     ./nvim-metals
@@ -46,7 +48,7 @@
       vim-commentary
       tabular
       vim-plugin-AnsiEsc
-    ] ++ (lib.optional config.isGui markdown-preview-nvim);
+    ] ++ (lib.optional opt.isGui markdown-preview-nvim);
 
     #MC Vim config
     extraConfig = ''
diff --git a/usr/cli/vim/nvim-metals/default.nix b/usr/cli/vim/nvim-metals/default.nix
index acb37c34..0af8cfe0 100644
--- a/usr/cli/vim/nvim-metals/default.nix
+++ b/usr/cli/vim/nvim-metals/default.nix
@@ -3,10 +3,11 @@
 #MC The JRE proxy need subtle configuration.
 { config, pkgs, ... }:
 let
+  opt = import ../../../../opt.nix;
   jre_with_proxy = pkgs.callPackage ./jre_with_proxy.nix {
     jre = pkgs.openjdk_headless;
     proxyHost = "127.0.0.1";
-    proxyPort = "${toString config.proxyPort}";
+    proxyPort = toString opt.proxyPort;
   };
   my-nvim-metals = {
     plugin = pkgs.vimPlugins.nvim-metals;
@@ -23,9 +24,9 @@ let
         excludedPackages = { "akka.actor.typed.javadsl", "com.github.swagger.akka.javadsl" },
         serverProperties = {
           "-Dhttps.proxyHost=127.0.0.1",
-          "-Dhttps.proxyPort=${toString config.proxyPort}",
+          "-Dhttps.proxyPort=${toString opt.proxyPort}",
           "-Dhttp.proxyHost=127.0.0.1",
-          "-Dhttp.proxyPort=${toString config.proxyPort}",
+          "-Dhttp.proxyPort=${toString opt.proxyPort}",
         },
         -- see `:h metalsBinaryPath`, "Another setting for you crazy Nix kids." Hahaha!
         metalsBinaryPath = "${pkgs.metals.override {jre = jre_with_proxy;}}/bin/metals",
@@ -59,9 +60,9 @@ in {
   home.file.jvmopts = {
     text = ''
       -Dhttps.proxyHost=127.0.0.1
-      -Dhttps.proxyPort=${toString config.proxyPort}
+      -Dhttps.proxyPort=${toString opt.proxyPort}
       -Dhttp.proxyHost=127.0.0.1
-      -Dhttp.proxyPort=${toString config.proxyPort}
+      -Dhttp.proxyPort=${toString opt.proxyPort}
     '';
     target = ".bloop/.jvmopts";
   };
diff --git a/usr/gui/gnome.nix b/usr/gui/gnome.nix
index 07718ad9..d2355c56 100644
--- a/usr/gui/gnome.nix
+++ b/usr/gui/gnome.nix
@@ -1,7 +1,9 @@
 { config, pkgs, stdenv, lib, ... }:
 # gnome extensions and settings
 # no need log out to reload extension: <alt>+F2 r
-{
+let
+  opt = import ../../opt.nix;
+in{
   home.packages = (with pkgs; [
     gnome.gnome-sound-recorder
     gnome.dconf-editor
@@ -187,9 +189,9 @@
 
     # proxy
     "system/proxy" = {mode = "manual";};
-    "system/proxy/ftp" = {host="127.0.0.1"; port=config.proxyPort;};
-    "system/proxy/http" = {host="127.0.0.1"; port=config.proxyPort;};
-    "system/proxy/https" = {host="127.0.0.1"; port=config.proxyPort;};
+    "system/proxy/ftp" = {host="127.0.0.1"; port=opt.proxyPort;};
+    "system/proxy/http" = {host="127.0.0.1"; port=opt.proxyPort;};
+    "system/proxy/https" = {host="127.0.0.1"; port=opt.proxyPort;};
 
     # input method
     "org/gnome/desktop/input-sources" = {