update README and the screenshot, closes #2

README.md

@@ -1,12 +1,12 @@
-# Firefox Gnome Theme (dark variant only... for now)
+# Firefox Gnome Theme
 
 ![Screenshot of the theme](screenshot.png)
 
 ## Description
 
 This is a bunch of CSS code to make Firefox 57+ look closer to GNOME's default
-dark theme. It styles the UI and interal Firefox' pages like about: and
-view-source:. I only wrote styles for the dark variant, not the light one.
+theme. It styles the UI and, if you pick the dark variant, interal Firefox'
+pages like about: and view-source:. Both light and dark variants are supported.
 
 ## Installation
 
@@ -21,14 +21,35 @@ Extensions can no longer style UI elements, but we can still use good old
 	git clone 'https://github.com/kurogetsusai/firefox-gnome-theme.git' chrome
 	```
 
-You must run Firefox with the dark theme, either by setting it globally as your
-default theme in GNOME Tweak Tools, or by running Firefox with the GTK_THEME
-variable like this:
+3. The GTK theme variant must match the variant you picked for this Firefox
+theme, which means you must either enable (for the dark variant) or disable (for
+the light one) global dark theme in GNOME Tweak Tools, or alternativelly, you
+can run Firefox with a specific variant without changing the global theme by
+supplying the GTK_THEME variable like this:
 
 	```sh
+	# for the dark theme
 	GTK_THEME=Adwaita:dark firefox
+
+	# for the light one
+	GTK_THEME=Adwaita:light firefox
 	```
 
+If you choose the light variant, you must also enable it in your
+`userChrome.css` file and disable the dark one. Just uncomment the
+`@import "ui/theme-light.css";` file and comment the
+`@import "ui/theme-dark.css";` one, so it looks like this:
+
+```css
+/* Dark theme */
+/*@import "ui/theme-dark.css"; /**/
+/* Light theme */
+@import "ui/theme-light.css"; /**/
+```
+
+The `userContent.css` file makes all the Firefox' internal pages dark, so if you
+don't want them dark, just remove that file.
+
 You might want to adjust your default link colors so they are more visible on
 dark background, either drop the code below into your
 `(firefox profile)/user.js` file or change them manually in `about:config`.
@@ -63,8 +84,8 @@ issues here on GitHub and share your ideas if you know how to fix them.
 
 ## Development
 
-If you wanna mess around the styles and change something, or create a light
-variant of this theme, you might find these things useful.
+If you wanna mess around the styles and change something, you might find these
+things useful.
 
 To use the Inspector to debug the UI, open the developer tools (F12) on any
 page, go to options, check both of those: