better offline docs

fixes https://github.com/tidalcycles/strudel/issues/424

website/src/pages/learn/pwa.mdx

@@ -7,5 +7,69 @@ layout: ../../layouts/MainLayout.astro
 
 You can use Strudel even without a network! When you first visit the [Strudel REPL](strudel.tidalcycles.org/),
 your browser will download the whole web app including documentation.
+When the download is finished (<1MB), you can visit the website even when offline,
+getting the downloaded website instead of the online one.
+
+When the site gets updated, your browser will download that update on the next online visit.
+When an update is available, the site will refresh after the download is finished.
+
+This works because Strudel is implemented as progessive web app (using [Vite PWA](https://vite-pwa-org.netlify.app/)).
+
+## Samples
+
+While the browser will download the app itself, samples are only downloaded when you're actively using them.
+So to make sure a specific set of samples is available when offline, just use them.
+Also, only samples from these domains will be cached for offline use:
+
+- `https://raw.githubusercontent.com/*` for samples uploaded to github
+- `https://freesound.org/*` / `https://cdn.freesound.org/*` for freesound
+- `https://shabda.ndre.gr/.*` for shabda
+
+## Inspecting / Clearing Cache
+
+You can view all cached files in your browser.
+
+### Firefox
+
+- Open the Developer Tools (`Tools > Web Developer > Web Developer Tools`)
+- go to `Storage` tab and expand `Cache Storage > https://strudel.tidalcycles.org`.
+- or go to the `Application` tab and view the latest updates in `Service Workers`
+
+### Chromium based Browsers
+
+- Open Developer Tools (`Right Click > Inspect`)
+- go to the `Application` tab
+- view downloaded files under `Cache > Cache Storage`
+- view the latest updates in `Service Workers`
+
+## Strudel Standalone App
+
+You can also install Strudel as a standalone app on most devices.
+A standalone app has its own desktop / homescreen icon and launches in a separate window,
+without the browser ui.
+
+### Desktop
+
+With a chromium based browser:
+
+1. go to the [Strudel REPL](strudel.tidalcycles.org/).
+2. on the right of the adress bar, click `install Strudel REPL`
+3. the REPL should now run as a standalone chromium app
+
+Without a chromium based browser, you can use [nativefier](https://github.com/nativefier/nativefier) to generate a desktop app:
+
+1. make sure you have NodeJS installed
+2. run `npx nativefier strudel.tidalcycles.org`
+
+### iOS
+
+1. open to the [Strudel REPL](strudel.tidalcycles.org/) in safari
+2. press the share icon and tab `Add to homescreen`
+3. You should now have a strudel app icon that opens the repl in full screen
+
+### Android
+
+1. open to the [Strudel REPL](strudel.tidalcycles.org/)
+2. Tab the install button at the bottom
 
 Ok, what are [Patterns](/technical-manual/patterns) all about?