-This is a (BD style) magic wall. It gets activated for a limited
-time by certain elements that fall on it. Objects falling though
-it will be changed to other objects. After it has stopped running,
-it cannot be activated again.
+This BD style magic wall converts rocks into diamonds and vice versa. Note that
+a magic wall can only be activated for some limited time. It can also turn mega
+rocks into nitro packs, nitro packs into mega rocks. Even flying diamonds and
+rocks pass them to be converted into each other, but they do that from bottom to
+up, of course.
+
+The duration in seconds for which magic walls are active is configurable.
+A duration of zero will let the wall run forever.
+All magic walls share the same timer.