Left and Right were wrong.

src/control_ui.cpp

@@ -113,10 +113,10 @@ void ControlUI::process_commands(std::shared_ptr<SlidesUI> slides) {
       full_screen(!$full_screen);
       break;
     case MOVE_LEFT:
-      move(1);
+      move(-1);
       break;
     case MOVE_RIGHT:
-      move(-1);
+      move(1);
       break;
     case NEXT_SLIDE:
       slides->next_slide();
@@ -154,10 +154,10 @@ void ControlUI::update(std::shared_ptr<SlidesUI> slides) {
       using KEY = sf::Keyboard::Scan;
       switch(key->scancode) {
         case KEY::A:
-          move(1);
+          move(-1);
           break;
         case KEY::D:
-          move(-1);
+          move(1);
           break;
         case KEY::Q:
           $controller.close();