+/* values for special move patterns (bits 0-3: basic move directions) */
+#define MV_BIT_TOWARDS_PLAYER 4
+#define MV_BIT_AWAY_FROM_PLAYER 5
+#define MV_BIT_ALONG_LEFT_SIDE 6
+#define MV_BIT_ALONG_RIGHT_SIDE 7
+#define MV_BIT_TURNING_LEFT 8
+#define MV_BIT_TURNING_RIGHT 9
+
+/* values for special move patterns for custom elements */
+#define MV_HORIZONTAL (MV_LEFT | MV_RIGHT)
+#define MV_VERTICAL (MV_UP | MV_DOWN)
+#define MV_ALL_DIRECTIONS (MV_HORIZONTAL | MV_VERTICAL)
+#define MV_ANY_DIRECTION (MV_ALL_DIRECTIONS)
+#define MV_TOWARDS_PLAYER (1 << MV_BIT_TOWARDS_PLAYER)
+#define MV_AWAY_FROM_PLAYER (1 << MV_BIT_AWAY_FROM_PLAYER)
+#define MV_ALONG_LEFT_SIDE (1 << MV_BIT_ALONG_LEFT_SIDE)
+#define MV_ALONG_RIGHT_SIDE (1 << MV_BIT_ALONG_RIGHT_SIDE)
+#define MV_TURNING_LEFT (1 << MV_BIT_TURNING_LEFT)
+#define MV_TURNING_RIGHT (1 << MV_BIT_TURNING_RIGHT)
+
+/* values for slippery property for custom elements */
+#define SLIPPERY_ANY_RANDOM 0
+#define SLIPPERY_ANY_LEFT_RIGHT 1
+#define SLIPPERY_ANY_RIGHT_LEFT 2
+#define SLIPPERY_ONLY_LEFT 3
+#define SLIPPERY_ONLY_RIGHT 4