Add newer Android styles

app/src/main/res/values-v21/styles.xml

@@ -0,0 +1,14 @@
+<resources>
+
+    <!--
+        Base application theme for API 21+. This theme completely replaces
+        AppBaseTheme from BOTH res/values/styles.xml and
+        res/values-v21/styles.xml on API 21+ devices.
+    -->
+    <style name="AppBaseTheme" parent="android:Theme.Material">
+        <!-- API 21 theme customizations can go here. -->
+        <item name="android:statusBarColor">#212121</item>
+        <item name="android:navigationBarColor">#212121</item>
+    </style>
+
+</resources>

app/src/main/res/values-v24/styles.xml

@@ -0,0 +1,12 @@
+<resources>
+
+    <!--
+      Use a black background to avoid the transparent background when switching apps.
+      android:windowBackgroundFallback is supposed to do this, but it wasn't working for
+      me as of Android 7.1
+    -->
+    <style name="StreamBaseTheme" parent="AppBaseTheme">
+        <item name="android:windowBackground">@android:color/black</item>
+    </style>
+
+</resources>

app/src/main/res/values-v29/styles.xml

@@ -0,0 +1,6 @@
+<resources>
+    <style name="AppBaseTheme" parent="android:Theme.Material">
+        <item name="android:navigationBarColor">@android:color/transparent</item>
+        <item name="android:statusBarColor">@android:color/transparent</item>
+    </style>
+</resources>