diff --git a/assets/views/fragments/.thumbnail-dt.jet.html.swp b/assets/views/fragments/.thumbnail-dt.jet.html.swp
new file mode 100644
index 0000000..616e429
Binary files /dev/null and b/assets/views/fragments/.thumbnail-dt.jet.html.swp differ
diff --git a/assets/views/fragments/thumbnail-dt.jet.html b/assets/views/fragments/thumbnail-dt.jet.html
index 5ccea25..ade0fb2 100644
--- a/assets/views/fragments/thumbnail-dt.jet.html
+++ b/assets/views/fragments/thumbnail-dt.jet.html
@@ -19,10 +19,11 @@
     <div class="artwork-page-count"><span>&#9654;</span></div>
     {{- end }}
   </div>
+  {{- AiType := isset(.AiType) ? .AiType : 0}}
   <a target="{{ target }}" href="/artworks/{{ .ID }}#checkpoint">
     {{- if (.XRestrict > 0 && hideR18 != "" && hideR18G != "") || (.XRestrict == 2 && hideR18G != "") }}
     <img src="/img/nsfw.png" alt="{{ .Title }}" loading="lazy" />
-    {{- else if .AiType == 2 && hideAi }}
+    {{- else if AiType == 2 && hideAi }}
     <img src="/img/ai.png" alt="{{ .Title }}" loading="lazy" />
     {{- else }}
     <img src="{{ .Thumbnail }}" alt="{{ .Title }}" loading="lazy" />
diff --git a/doc/dev/.guidelines.md.kak.YMWRiB b/doc/dev/.guidelines.md.kak.YMWRiB
new file mode 100644
index 0000000..170c09e
--- /dev/null
+++ b/doc/dev/.guidelines.md.kak.YMWRiB
@@ -0,0 +1,9 @@
+# File structure
+
+- `assets/`: Static files (images, CSS, JS) and site templates.
+- `config/`: Handle configurations for the server.
+	- `config.go`: Parses for environment variables and pass down the configurations.
+	- `proxy_list.go`: Contains the built-in third party image proxy list.
+- `core/`: Make requests to Pixiv's server and parses information into structured data.
+- `doc/`: Contains documentations for the general user and developers.
+- `server/`: 
diff --git a/doc/dev/guidelines.md b/doc/dev/guidelines.md
new file mode 100644
index 0000000..44c7b08
--- /dev/null
+++ b/doc/dev/guidelines.md
@@ -0,0 +1,18 @@
+This file contains guidelines for code development.
+
+# File structure
+
+- `assets/`: Static files (images, CSS, JS) and site templates.
+- `config/`: Handle configurations for the server.
+  - `config.go`: Parses for environment variables and pass down the configurations.
+  - `proxy_list.go`: Contains the built-in third party image proxy list.
+- `core/`: Make requests to Pixiv's server and parses information into structured data.
+- `doc/`: Contains documentations for the general user and developers.
+- `server/`: The web server.
+  - `audit/`: Audit requests made by PixivFE to external APIs.
+  - `handlers/`: Contains middlewares for logging, rate limiting, error handling, etc.
+  - `proxy_checker/`: The image proxy checker.
+  - `routes/`: Routes handling. Pages will be rendered here.
+  - `session/`: Handles user's options.
+  - `template/`: Core template renderer and template functions.
+  - `utils/`: Other utilities.