+#define UP_and_DOWN(d) \
+ Direction d = UP; d != CENTER; d = (d == UP ? DOWN : CENTER)
+
+#define DOWN_and_UP(d) \
+ Direction d = DOWN; d != CENTER; d = (d == DOWN ? UP : CENTER)
+
+#define LEFT_and_RIGHT(d) \
+ Direction d = LEFT; d != CENTER; d = (d == LEFT ? RIGHT : CENTER)
+