diff --git a/src/window.vala b/src/window.vala
index 9bbe6f1..c5eea4b 100644
--- a/src/window.vala
+++ b/src/window.vala
@@ -1,37 +1,60 @@
 public class WriteAs.MainWindow : Gtk.ApplicationWindow {
     private Gtk.TextView canvas;
 
+    private bool dark_mode = false;
+
     construct {
         construct_toolbar();
 
         canvas = new Gtk.TextView();
         add(canvas);
     }
 
     public MainWindow(Gtk.Application app) {
         set_application(app);
 
         set_default_size(800, 600);
     }
 
     private void construct_toolbar() {
         var header = new Gtk.HeaderBar();
         header.title = "";
         header.show_close_button = true;
         set_titlebar(header);
 
         var darkmode_button = new Gtk.ToggleButton();
         // NOTE the fallback icon is a bit of a meaning stretch, but it works.
         var icon_theme = Gtk.IconTheme.get_default();
         darkmode_button.image = new Gtk.Image.from_icon_name(
                 icon_theme.has_icon("writeas-bright-dark") ?
                     "writeas-bright-dark" : "weather-clear-night",
                 Gtk.IconSize.SMALL_TOOLBAR);
         darkmode_button.draw_indicator = false;
         var settings = Gtk.Settings.get_default();
         darkmode_button.toggled.connect(() => {
             settings.gtk_application_prefer_dark_theme = darkmode_button.active;
+            dark_mode = darkmode_button.active;
+            adjust_text_style();
         });
         header.pack_end(darkmode_button);
     }
+
+    private Gtk.CssProvider cur_styles = null;
+    private void adjust_text_style() {
+        try {
+            var styles = canvas.get_style_context();
+            if (cur_styles != null) styles.remove_provider(cur_styles);
+
+            var css = "";
+            if (dark_mode) {
+                css = "* {background: black; color: white;}";
+            }
+            cur_styles = new Gtk.CssProvider();
+            cur_styles.load_from_data(css);
+
+            styles.add_provider(cur_styles, Gtk.STYLE_PROVIDER_PRIORITY_APPLICATION);
+        } catch (Error e) {
+            warning(e.message);
+        }
+    }
 }