摄像机系统，和子对象绑定

include/camera.hpp

@@ -0,0 +1,20 @@
+#pragma once
+
+#include <string>
+
+#include <actor.hpp>
+
+namespace boundard {
+
+class Camera : public Actor {
+   public:
+    Camera(std::string name, Game& game) : Actor(std::move(name), game) {}
+
+    float zoom() const { return zoom_; }
+    void set_zoom(float zoom) { zoom_ = zoom > 0.0F ? zoom : 0.0001F; }
+
+   private:
+    float zoom_ = 1.0F;
+};
+
+}  // namespace boundard