feat: add snapshot recording

src/vec.py

@@ -8,6 +8,9 @@ class Vec:
         self.x: float = x
         self.y: float = y
 
+    def copy(self) -> Vec:
+        return Vec(self.x, self.y)
+
     def __add__(self, other: float | Vec) -> Vec:
         if isinstance(other, Vec):
             return Vec(self.x + other.x, self.y + other.y)