A board game of Thud! was released several years ago. The rules are available online
On the dwarfs' turn, they may either move or hurl one dwarf:
Move: any one dwarf is moved like a chess queen, any number of squares
in any orthogonal or diagonal direction, but not onto or through any
other piece, whether Thudstone, dwarf, or troll;
or
Hurl: anywhere
there is a straight (orthogonal or diagonal) line of adjacent dwarfs
on the board, they may hurl the front dwarf in the direction
continuing the line, as long as the space between the lead dwarf and
the troll is less than the number of dwarfs in the line. This is
different from a normal move in that the dwarf is permitted to land on
a square containing a troll, in which case the troll is removed from
the board and the dwarf takes his place. This may only be done if the
endmost dwarf can land on a troll by moving in the direction of the
line at most as many spaces as there are dwarfs in the line. Since a
single dwarf is a line of one in any direction, a dwarf may always
move one space to capture a troll on an immediately adjacent square.
On the trolls' turn, they may either move or shove one troll:
Move: one troll is moved like a chess king, one square in any
orthogonal or diagonal direction onto an empty square. After the troll
has been moved, only a single dwarf on the eight squares adjacent to
the moved troll may optionally be immediately captured and removed
from the board, at the troll player's discretion;
or
Shove: anywhere
there is a straight (orthogonal or diagonal) line of adjacent trolls
on the board, they may shove the endmost troll in the direction
continuing the line, up to as many spaces as there are trolls in the
line. As in a normal move, the troll may not land on an occupied
square, and any (all) dwarfs in the eight squares adjacent to its
final position may immediately be captured. Trolls may only make a
shove if by doing so they capture at least one dwarf.
The battle is
over when both players agree that no more captures can be made by
continuing to play, or when one player has no more valid moves to
make. At this point the players count score: the dwarfs score 1 point
for each surviving dwarf, and the trolls score 4 for each remaining
troll, with the difference being the 'final' score. The players should
then swap sides to play another round, and the sum of their final
scores for the two battles determines the overall victor.