feat(tpl): Complete rework of the app-down template

README.md

@@ -79,9 +79,13 @@ The following templates are built-in and available for use without any additiona
 > The `cats` template is the only one of those that fetches resources (the actual cat pictures) from external
 > servers - all other templates are self-contained.
 
+> [!TIP]
+> If you need the **pre-rendered static error pages pack**, you can download it as a [zip][pages-pack-zip] or
+> [tar.gz][pages-pack-tar-gz] archive.
+
 [app-down-link]:https://tarampampam.github.io/error-pages/app-down/404.html
-[app-down-light]:https://github.com/tarampampam/error-pages/assets/7326800/ad4b4fd7-7c7b-4bdc-a6b6-44f9ba7f77ca
-[app-down-dark]:https://github.com/tarampampam/error-pages/assets/7326800/4e668a56-a4c4-47cd-ac4d-b6b45db54ab8
+[app-down-light]:https://github.com/user-attachments/assets/c5f42b53-51cd-47c4-a22f-553d44d2a288
+[app-down-dark]:https://github.com/user-attachments/assets/135bac8c-983f-461c-97ba-e653e9b9adfe
 [cats-link]:https://tarampampam.github.io/error-pages/cats/404.html
 [cats-light]:https://github.com/tarampampam/error-pages/assets/7326800/056cd00e-bc9a-4120-8325-310d7b0ebd1b
 [cats-dark]:https://github.com/tarampampam/error-pages/assets/7326800/5689880b-f770-406c-81dd-2d28629e6f2e
@@ -134,10 +138,6 @@ Download the latest binary for your OS/architecture from the [releases page][lat
 Supported image architectures - `linux/amd64`, `linux/arm/v7`, `linux/arm64`, `linux/ppc64le`, `linux/s390x`.
 All images are signed with [Cosign][cosign] using keyless signing (GitHub OIDC).
 
-> [!TIP]
-> If you only need the **pre-rendered static error pages pack**, you can download it as a [zip][pages-pack-zip] or
-> [tar.gz][pages-pack-tar-gz] archive.
-
 ### 📦 Helm chart
 
 A Helm chart for Kubernetes is included with each release ([download][latest-helm-chart]), published on
@@ -297,8 +297,12 @@ go build ./cmd/error-pages/ && go build ./cmd/builder/ # build both binaries
 go test -race ./...                       # run all tests
 golangci-lint run --fix                   # lint the code and apply any available auto fixes
 helm-docs -c ./deploy/helm/ -t README.tpl.md -o README.md # regenerate chart readme file
-watchexec -r -- go run ./cmd/error-pages/ # run a live reloading server (useful for testing template changes)
-your_ai_tool --prompt "explain why AI Coding Agents are doing shit by default" # before vibe-coding
+
+# run a live reloading server (useful for testing template changes)
+watchexec -r -- go run ./cmd/error-pages/ --show-details
+
+# run before every vibe-coding session
+your_ai_tool --prompt "explain why AI Coding Agents are doing shit by default"
 ```
 
 ## 🧑‍🤝‍🧑 Contributors

docs/templating.md

@@ -3,6 +3,29 @@
 Templates are parsed **once at startup**. The same template engine is used for all output formats. When a custom
 HTML template is set via `--html-template`, the `--template-name` and `--rotation-mode` flags are ignored.
 
+### Go template primer
+
+Error pages uses the standard Go [`text/template`][go-text-template] package (with HTML output treated as text to
+preserve full control over markup). If you have never written a Go template before, do not worry - it is genuinely one
+of the **simplest** templating languages around. The full mental model fits in a few minutes.
+
+**Key concepts:**
+
+- `{{ }}` - action delimiters; everything outside them is emitted verbatim.
+- `{{ .Field }}` - output a field from the data object (`.` is "current value").
+- `{{ if .Cond }} ... {{ else }} ... {{ end }}` - conditional.
+- `{{ range .Slice }} {{ . }} {{ end }}` - iteration (`.` becomes each element).
+- `{{ .Value | funcName }}` - pipeline; passes the value on the left as the last argument to the function on the right.
+- `{{ /* comment */ }}` - comment (not emitted).
+
+**Documentation**:
+
+- [`text/template` package - the complete, authoritative reference][go-text-template].
+- [Go Templates Guide](https://hackmd.io/@gekart/go-templates?utm_source=chatgpt.com) - syntax explained with
+  examples (recommended for beginners).
+
+[go-text-template]: https://pkg.go.dev/text/template
+
 > [!WARNING]
 > `{{` and `}}` are reserved as Go template delimiters - any literal occurrence causes a parse error. This is
 > common in JSDoc type annotations (`/** @param {{ id: number }} ❌ */`), CSS, etc. To work around this, you can simply
@@ -81,3 +104,5 @@ HTML pages support automatic **client-side localization** in 15+ languages, temp
 The browser detects the visitor's preferred language via `navigator.languages` and translates all `[data-l10n]`
 elements in-place - no server round-trip required. Localization can be disabled globally with `--disable-l10n`
 (or via env `DISABLE_L10N=true`).
+
+You can find more details on handling localization in templates in the [Localization documentation](../l10n/readme.md).