<!-- nornir:class: guide -->
# For idiots — About + the demo button, in plain words
> **Class:** `guide` (beginner). Design: [`common-framework-design.md`](common-framework-design.md).
## The big idea
All the nordisk apps (nornir, dwarves, korp, holger) are built to feel the same — like
how every JetBrains app has the same menus. They **share** the plumbing instead of each
copying it:
- one way to install/start/stop the service (skidbladnir),
- one network server loop (nornir-service),
- one **job manager** that tracks background work and can start containers (jera),
- one UI toolkit (facett).
holger already used most of that. This work added the pieces it was missing in its
window: an **About** box, a **demo button** that uses the shared job manager, the shared
**tab shell** (which also shrinks nicely on a small screen), and a **Sign in** box — all
borrowed from the shared UI toolkit instead of hand-built.
## About box
Click **ℹ About** at the top. A little window shows holger's logo, name, version, and
the list of shared pieces it's built on. Click **Close** to dismiss it. That's it.
## Sign in box
There's a **Sign in** tab. Click it and you get a code + a web link: open the link, type
the code, and you're signed in — the same little sign-in box korp uses (it's borrowed, not
re-built). holger only ever shows **who** you are, never your actual password or token.
## Small screens
On a narrow window the top row of switches tucks itself behind one **⚙ Controls** button
so the main area still has room. Make the window wide again and the switches come back.
## The demo button
Go to the **Tools** tab and pick **6 · demo appliance**. Click **Start demo
appliance…**. holger asks the shared job manager (jera) to start a small demo package
registry in a container.
- Normally it just **writes down the job** ("I would start this container") and shows
you a job id — no container software needed on your laptop.
- If you start holger the special way (`--features gui,containers`), it **actually
starts** the container, and you can open `http://127.0.0.1:5000`.
Why through the job manager and not "just start it"? So there's always a **record** of
what was started, exactly like every other app in the family. No hidden background
threads.