split out sandboxed Google Play section

static/features.html

@@ -88,6 +88,7 @@
                     <li>
                         <a href="#grapheneos">GrapheneOS</a>
                         <ul>
+                            <li><a href="#sandboxed-google-play">Sandboxed Google Play</a></li>
                             <li><a href="#more-complete-patching">More complete patching</a></li>
                             <li><a href="#disabling-secondary-user-app-installation">Disabling secondary
                             user app installation</a></li>
@@ -310,11 +311,47 @@
                     they avoid requiring invasive OS integration. Building privileged support for
                     Google services into the OS isn't something we're going to be doing, even if
                     that's partially open source like microG.</li>
-                    <li><a href="/usage#sandboxed-google-play">Compatibility layer for coercing
-                    user installed Google Play services into running as sandboxed apps without any
-                    special privileges.</a></li>
                 </ul>
 
+                <section id="sandboxed-google-play">
+                    <h3><a href="#sandboxed-google-play">Sandboxed Google Play</a></h3>
+
+                    <p>GrapheneOS has a compatibility layer providing the option to install and use
+                    the official releases of Google Play in the standard app sandbox. Google Play
+                    receives absolutely no special access or privileges on GrapheneOS as opposed to
+                    bypassing the app sandbox and receiving a massive amount of highly privileged
+                    access. Instead, the compatibility layer teaches it how to work within the full
+                    app sandbox. It also isn't used as a backend for the OS services as it would be
+                    elsewhere since GrapheneOS doesn't use Google Play even when it's installed.</p>
+
+                    <p>Since the Google Play apps are simply regular apps on GrapheneOS, you install
+                    them within a specific user or work profile and they're only available within that
+                    profile. Only apps within the same profile can use it and they need to explicitly
+                    choose to use it. It works the same way as any other app and has no special
+                    capabilities. As with any other app, it can't access data of other apps and
+                    requires explicit user consent to gain access to profile data or the standard
+                    permissions. Apps within the same profile can communicate with mutual consent and
+                    it's no different for sandboxed Google Play.</p>
+
+                    <p>The core functionality and APIs are almost entirely supported already since
+                    GrapheneOS largely only has to coerce these apps into continuing to run without
+                    being able to use any of the usual invasive OS integration. A compatibility layer
+                    is also provided to support dynamically downloaded/loaded modules (dynamite
+                    modules). The compatibility layer will be gradually expanded and improved in order
+                    to get more of the Google Play functionality working.</p>
+
+                    <p>GrapheneOS provides a dedicated compatibility layer for Play Store app
+                    installation/updates/removal teaching it to use the standard unprivileged approach
+                    available to sandboxed apps. It prompts the user to permit it as an app source and
+                    then prompts for the initial app install/update or removal. It will use Android
+                    12's support for unattended updates when possible which means it can do unattended
+                    updates of modern (API 29+) apps where it was the installer for the currently
+                    installed version already.</p>
+
+                    <p>See the <a href="/usage#sandboxed-google-play-installation">usage guide
+                    section on sandboxed Google Play</a> for instructions.</p>
+                </section>
+
                 <section id="more-complete-patching">
                     <h3><a href="#more-complete-patching">More complete patching</a></h3>
 

static/usage.html

@@ -813,6 +813,9 @@
             <section id="sandboxed-google-play">
                 <h2><a href="#sandboxed-google-play">Sandboxed Google Play</a></h2>
 
+                <!-- keep in sync with features.html since we aren't simply linking to
+                    features.html to avoid people skipping this important explanation -->
+
                 <p>GrapheneOS has a compatibility layer providing the option to install and use
                 the official releases of Google Play in the standard app sandbox. Google Play
                 receives absolutely no special access or privileges on GrapheneOS as opposed to