<s>
MUD2	B-Protocol
is	O
the	O
successor	O
of	O
MUD1	B-Protocol
,	O
Richard	O
Bartle	O
's	O
pioneering	O
Multi-User	B-Application
Dungeon	I-Application
.	O
</s>
<s>
Character	O
progress	O
up	O
a	O
ladder	O
of	O
11	O
levels	O
until	O
they	O
reach	O
the	O
traditional	O
MUD	B-Application
goal	O
of	O
wiz	O
(	O
wizard	O
or	O
witch	B-Device
)	O
.	O
</s>
<s>
Much	O
of	O
MUD2	B-Protocol
's	O
long-running	O
appeal	O
comes	O
from	O
its	O
much-celebrated	O
depth	O
,	O
and	O
its	O
wide-ranging	O
gameplay	O
,	O
as	O
it	O
contains	O
large	O
elements	O
of	O
puzzle-solving	O
and	O
exploration	O
,	O
as	O
well	O
as	O
elements	O
of	O
skill	O
,	O
chance	O
,	O
and	O
humour	O
.	O
</s>
