Make the raycaster 'highlight' things you point at.

raycaster.cpp

@@ -187,6 +187,7 @@ void Raycaster::sprite_casting(sf::RenderTarget &target) {
         apply_sprite_effect(effect, sprite_width, sprite_height);
       } else {
         effect = $brightness;
+        level += (aiming_at == rec.second) * 0.1;
         effect->setUniform("darkness", level);
       }