add ship, improve inheritance

src/Entity.h

@@ -1,8 +1,5 @@
 #pragma once
-#include <cctype>
-#include <ncurses.h>
 #include <string>
-#include <unordered_map>
 #include <vector>
 
 struct AssetPair {
@@ -21,4 +18,12 @@ public:
 
   float getX() const noexcept { return x; }
   float getY() const noexcept { return y; }
+
+  virtual void update() noexcept = 0;
+  virtual bool isOffScreen() const noexcept = 0;
+  virtual const std::vector<std::string> &getImage() const = 0;
+  virtual const std::vector<std::string> &getMask() const = 0;
+  virtual char getDefaultColor() const noexcept = 0;
+
+  void draw(int layer) const;
 };