Quick fix for the clock to not start right away.

sfmlbackend.hpp

@@ -56,7 +56,7 @@ class SFMLBackend {
   sf::Sprite start_button;
   sf::Texture start_texture;
   std::chrono::time_point<std::chrono::system_clock> clock_start;
-  Button buttons = Button::NONE;
+  Button buttons = Button::STOP;
   int hit_points = 50;
   sf::Font font;
   GameEngine &game;