add main_camera script

scripts/main_camera.gd

@@ -0,0 +1,19 @@
+extends Camera3D
+
+var mouse_position: Vector2 = Vector2(0, 0)
+
+func _process(delta: float) -> void:
+	var viewport_size := get_viewport().get_visible_rect().size
+
+	if (mouse_position.x == 0):
+		print('left!')
+	if (mouse_position.x == viewport_size.x - 1):
+		print('right!')
+	if (mouse_position.y == 0):
+		print('top!')
+	if (mouse_position.y == viewport_size.y - 1):
+		print('bottom!')
+
+func _input(event: InputEvent) -> void:
+	if event is InputEventMouseMotion:
+		mouse_position = (event as InputEventMouseMotion).position