add restart button to game over screen

src/ui/MainWindow.cpp

@@ -2,6 +2,7 @@
 
 #include <QHBoxLayout>
 #include <QMessageBox>
+#include <QPushButton>
 #include <QResizeEvent>
 #include <QVBoxLayout>
 
@@ -106,7 +107,17 @@ void MainWindow::onGameOver()
     box.setText(QString("HQ destroyed!\nSurvival time: %1:%2")
         .arg(minutes, 2, 10, QChar('0'))
         .arg(seconds, 2, 10, QChar('0')));
+    QPushButton* restartBtn = box.addButton("Restart", QMessageBox::AcceptRole);
     box.addButton("Quit", QMessageBox::RejectRole);
     box.exec();
-    close();
+
+    if (box.clickedButton() == restartBtn)
+    {
+        m_sim->reset();
+        m_gameWorldView->resetForNewGame();
+    }
+    else
+    {
+        close();
+    }
 }