-#define MV_DIR_BIT(x) ((x) == MV_LEFT ? MV_BIT_LEFT : \
- (x) == MV_RIGHT ? MV_BIT_RIGHT : \
- (x) == MV_UP ? MV_BIT_UP : MV_BIT_DOWN)
-
+#define MV_DIR_FROM_BIT(x) ((x) < NUM_DIRECTIONS ? 1 << (x) : \
+ (x) == MV_BIT_UPLEFT ? MV_UPLEFT : \
+ (x) == MV_BIT_UPRIGHT ? MV_UPRIGHT : \
+ (x) == MV_BIT_DOWNLEFT ? MV_DOWNLEFT : \
+ (x) == MV_BIT_DOWNRIGHT ? MV_DOWNRIGHT : \
+ MV_NONE)
+
+#define MV_DIR_TO_BIT(x) ((x) == MV_LEFT ? MV_BIT_LEFT : \
+ (x) == MV_RIGHT ? MV_BIT_RIGHT : \
+ (x) == MV_UP ? MV_BIT_UP : \
+ (x) == MV_DOWN ? MV_BIT_DOWN : \
+ (x) == MV_UPLEFT ? MV_BIT_UPLEFT : \
+ (x) == MV_UPRIGHT ? MV_BIT_UPRIGHT : \
+ (x) == MV_DOWNLEFT ? MV_BIT_DOWNLEFT : \
+ (x) == MV_DOWNRIGHT ? MV_BIT_DOWNRIGHT : \
+ MV_BIT_DOWN)
+
+#define MV_DIR_OPPOSITE(x) ((x) == MV_LEFT ? MV_RIGHT : \
+ (x) == MV_RIGHT ? MV_LEFT : \
+ (x) == MV_UP ? MV_DOWN : \
+ (x) == MV_DOWN ? MV_UP : \
+ (x) == MV_UPLEFT ? MV_DOWNRIGHT : \
+ (x) == MV_UPRIGHT ? MV_DOWNLEFT : \
+ (x) == MV_DOWNLEFT ? MV_UPRIGHT : \
+ (x) == MV_DOWNRIGHT ? MV_UPLEFT : \
+ MV_NONE)