-/* Try to move "monster" in random direction. On contact with other monster,
- * only bump. On contact with player, fight / reduce player's hitpoints,
- * and thereby potentially trigger the player's death. Update the log for any
- * contact action.
+/* Try to move "actor" one step in direction "d" (where east is 'E', north 'N'
+ * etc.) and handle the consequences: either the move succeeds, or another actor
+ * is encountered and hit (which leads to its lifepoint decreasing by one and
+ * potentially its death), or the target square is not passable, the move fails.