-/* Return yx_uint8 coordinate one step from "yx" in direction "dir" (numpad
- * digits: north '8', east: '6', etc.) If "dir" is invalid or would wrap the
- * move around the edge of a 2^16x2^16 cells field, "yx" remains unchanged.
+/* Move "yx" into hex direction "d". If this moves "yx" beyond the minimal (0)
+ * or maximal (UINT8_MAX) column or row, it wraps to the opposite side. Such
+ * wrapping is returned as a wraps enum value and stored, so that further calls
+ * to move "yx" back into the opposite direction may unwrap it again. Pass an
+ * "unwrap" of !0 to re-set the internal wrap memory to 0.
+ * Hex direction values for "d": 'e' (north-east), 'd' (east), 'c' (south-east),
+ * 'x' (south-west), 's' (west), 'w' (north-west)