diff --git a/main.c b/main.c
index 1df550f..a40da04 100644
--- a/main.c
+++ b/main.c
@@ -31,15 +31,21 @@ typedef struct _builderWidget {
     GtkWidget **widget;
 }builderWidget;
 
-typedef struct _flasher {
+struct flasher {
+    gboolean is_active;
     GtkWidget **progressBar;
     GtkWidget **fileEntry;
     GtkWidget **portEntry;
-}flasher;
+};
 
 
 static gboolean main_window_close(GtkWidget *widget, gpointer foo)
 {
+    struct flasher *flash = (struct flasher *)foo;
+    if (flash->is_active == TRUE) {
+        g_print("Flashing operation in progress. Can't close window.\n");
+        return TRUE;
+    }
     gtk_widget_destroy(widget);
     gtk_main_quit();
     return TRUE;
@@ -61,7 +67,9 @@ int main(int argc, char *argv[]) {
     static GtkWidget *portEntry;
     static GtkWidget *progressBar;
     static GtkWidget *fileDialog;
-    static flasher stmFlasher;
+    static struct flasher stmFlasher =
+    {   .is_active = FALSE
+    };
 
     static parameter progParams[] = {
         {
@@ -71,38 +79,38 @@ int main(int argc, char *argv[]) {
         },
         {.name = "--port",.hasValue = hasVal,.value = (void*)port},{.name = "--file",.hasValue = hasVal,.value = (void*)fileName},{.name = NULL}};
     static builderWidget builderWidgets[] = {
-      {
-          .widgetId = "startButton",
-          .widget = &startButton
-      },
-      {
-          .widgetId = "fileDialogButton",
-          .widget = &fileDialogButton
-      },
-      {
-          .widgetId = "fileEntry",
-          .widget = &fileEntry
-      },
-      {
-          .widgetId = "portEntry",
-          .widget = &portEntry
-      },
-      {
-          .widgetId = "progressBar",
-          .widget = &progressBar
-      },
-      {
-          .widgetId = "Dialog",
-          .widget = &fileDialog
-      }, 
-      {
-          .widgetId = "mainWindow",
-          .widget = &main_window
-      },
-      {
-          .widgetId = NULL,
-          .widget = NULL
-      }
+        {
+            .widgetId = "startButton",
+            .widget = &startButton
+        },
+        {
+            .widgetId = "fileDialogButton",
+            .widget = &fileDialogButton
+        },
+        {
+            .widgetId = "fileEntry",
+            .widget = &fileEntry
+        },
+        {
+            .widgetId = "portEntry",
+            .widget = &portEntry
+        },
+        {
+            .widgetId = "progressBar",
+            .widget = &progressBar
+        },
+        {
+            .widgetId = "Dialog",
+            .widget = &fileDialog
+        },
+        {
+            .widgetId = "mainWindow",
+            .widget = &main_window
+        },
+        {
+            .widgetId = NULL,
+            .widget = NULL
+        }
     };
 
     GtkBuilder *builder;
@@ -110,19 +118,23 @@ int main(int argc, char *argv[]) {
 
     parseParams(progParams, argc, argv);
     // Create flasher and fill elements
+    // TODO: remove widgets from flasher. use strings instead
     stmFlasher.fileEntry = &fileEntry;
     stmFlasher.portEntry = &portEntry;
     // TODO: above
-    gui = 1;
+
     if (gui) {
         gtk_init(&argc, &argv);
+        g_object_set(gtk_settings_get_default(),
+            "gtk-application-prefer-dark-theme", TRUE,
+            NULL);
         builder = gtk_builder_new();
         gtk_builder_add_from_file(builder, "window.glade", NULL);
 
         //Get Widgets from Builder
         parseBuilder(builder, builderWidgets);
         g_signal_connect(startButton, "clicked", G_CALLBACK(startFlash), &stmFlasher);
-        g_signal_connect(main_window, "delete-event", G_CALLBACK(main_window_close), NULL);
+        g_signal_connect(main_window, "delete-event", G_CALLBACK(main_window_close), &stmFlasher);
         gtk_main();
     } else {
         startFlash(&stmFlasher);
@@ -134,7 +146,7 @@ int main(int argc, char *argv[]) {
 
 
 
-void startFlash(flasher *flashObj) {
+void startFlash(struct flasher *flashObj) {
     printf("Flasher started\n");
     return;
 }
diff --git a/window.glade b/window.glade
index e3d1497..db418fd 100644
--- a/window.glade
+++ b/window.glade
@@ -65,6 +65,9 @@
                 <property name="visible">True</property>
                 <property name="can_focus">True</property>
                 <property name="receives_default">True</property>
+                <style>
+                  <class name="suggested-action"/>
+                </style>
               </object>
               <packing>
                 <property name="expand">False</property>
@@ -120,6 +123,9 @@
             <property name="visible">True</property>
             <property name="can_focus">True</property>
             <property name="receives_default">True</property>
+            <style>
+              <class name="suggested-action"/>
+            </style>
           </object>
           <packing>
             <property name="expand">True</property>