-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 is a BD style magic wall. It gets activated for a limited duration by
+rocks or gems that fall on it. While activated, they can fall through it, and
+rocks turn into BD style diamonds, and gems turn into BD style rocks.
+After the magic wall has stopped running, it cannot be activated again.
+
+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.