Refactored for x,y to be center of object and allow for scale multiplier. Also added code to handle the fact that curses can't print off the left size of the screen.

main.cpp

@@ -3,14 +3,14 @@
 #include <unistd.h> // usleep
 
 struct Object {
-	int x1, y1; // top left
-	int x2, y2; // bottom right
+	int x, y; // center
+	int width, height; // full, not half
 	double scale;
 
-	int Left()   const { return x1; }
-	int Right()  const { return x2; }
-	int Top()    const { return y1; }
-	int Bottom() const { return y2; }
+	int Left()   const { return x - (width  / 2.0) * scale; }
+	int Right()  const { return x + (width  / 2.0) * scale; }
+	int Top()    const { return y - (height / 2.0) * scale; }
+	int Bottom() const { return y + (height / 2.0) * scale; }
 };
 
 bool InBounds(Object bounds, Object object);
@@ -25,43 +25,61 @@ int main(int argc, char *argv[])
 	}
 
 	Object screen;
-	screen.x1 = 10;
-	screen.x2 = 31;
-	screen.y1 = 10;
-	screen.y2 = 15;
+	screen.x = 20;
+	screen.width = 20;
+	screen.y = 13;
+	screen.height = 6;
 	screen.scale = 1.0;
 
 	const Object initial_screen = screen;
 
 	Object object;
-	object.x1 = 1;
-	object.x2 = 5;
-	object.y1 = 4;
-	object.y2 = 8;
+	object.x = 3;
+	object.width = 5;
+	object.y = 6;
+	object.height = 4;
 	object.scale = 1.0;
 
 	const Object initial_object = object;
 
+	double scale_multiplier = 0.2;
+
 	while(true)
 	{
 		screen = initial_screen;
 		object = initial_object;
 
+		object.scale *= scale_multiplier;
+		scale_multiplier *= 2;
+
+		// NOTE: This causes it to pause on each resize when it is immediately covered.
+		//       To avoid this, move this initialization outside of the "while(true)" loop.
 		bool covered_last_frame = false;
 
-		for(auto y = 0; y < 14; ++y)
+		const int num_rows = 14;
+		for(auto r = 0; r < num_rows; ++r)
 		{
-			for(auto x = 0; x < 40; ++x)
+			const int num_columns = 40;
+			for(auto c = 0; c < num_columns; ++c)
 			{
 				// DRAW
 				clear();
-				std::string scr(screen.Right() - screen.Left() + 1, '+');
+				int left;
+				left = screen.Left();
+				if(left < 0)
+					left = 0;
+				// NOTE: +1 to account for full width
+				std::string scr(screen.Right() - left + 1, '+');
 				for(auto row = screen.Top(); row <= screen.Bottom(); ++row)
-					mvaddstr(row, screen.Left(), scr.c_str());
+					mvaddstr(row, left, scr.c_str());
 
-				std::string obj(object.Right() - object.Left() + 1, '*');
+				left = object.Left();
+				if(left < 0)
+					left = 0;
+				// NOTE: +1 to account for full width
+				std::string obj(object.Right() - left + 1, '*');
 				for(auto row = object.Top(); row <= object.Bottom(); ++row)
-					mvaddstr(row, object.Left(), obj.c_str());
+					mvaddstr(row, left, obj.c_str());
 
 				bool covered = InBounds(screen, object);
 
@@ -69,20 +87,18 @@ int main(int argc, char *argv[])
 
 				refresh();
 
+				// When there is a change in "covered" status, freeze to show it:
 				if(covered != covered_last_frame)
-					usleep(500000); // 1/2 sec
+					usleep(300000); // 3/10 sec
 				else
-					usleep(35000); // quick
+					usleep(5000); // quick (adjust to your PC's performance)
 
 				covered_last_frame = covered;
 
-				++object.x1;
-				++object.x2;
+				++object.x;
 			}
-			++object.y1;
-			++object.y2;
-			object.x1 -= 40;
-			object.x2 -= 40;
+			++object.y;
+			object.x -= num_columns;
 		}
 	}