// Monsters still under development
        || new_mclass == MONS_ROCK_WORM

static bool _find_wall_target(monsters *mon)
{
    ASSERT(mons_wall_shielded(mon));
    if (mon->travel_target == MTRAV_WALL)
    {
        coord_def targ_pos(mon->travel_path[mon->travel_path.size() - 1]);
        // Target grid might have changed since we started, like if the
        // player destroys the wall the monster wants to hide in.
        if (grid_is_solid(targ_pos)
            && monster_habitable_grid(mon, grd(targ_pos)))
        {
            // Wall is still good.
#ifdef DEBUG_PATHFIND
            mprf("%s target is (%d, %d), dist = %d",
                 mon->name(DESC_PLAIN, true).c_str(),
                 targ_pos.x, targ_pos.y, (int) (mon->pos() - targ_pos).rdist());
#endif
            return (true);
        }
        mon->travel_path.clear();
        mon->travel_target = MTRAV_NONE;
    }
    monster_los lm;
    lm.set_monster(mon);
    lm.set_los_range(LOS_RADIUS);
    lm.fill_los_field();
    int       best_dist             = INT_MAX;
    bool      best_closer_to_player = false;
    coord_def best_target;
    for (radius_iterator ri(mon->pos(), LOS_RADIUS, true, false);
         ri; ++ri)
    {
        if (!grid_is_solid(*ri)
            || monster_habitable_grid(mon, grd(*ri)))
        {
            continue;
        }
        int  dist = (mon->pos() - *ri).rdist();
        bool closer_to_player = false;
        if (dist > (you.pos() - *ri).rdist())
            closer_to_player = true;
        if (dist < best_dist)
        {
            best_dist             = dist;
            best_closer_to_player = closer_to_player;
            best_target           = *ri;
        }
        else if (best_closer_to_player && !closer_to_player
                 && dist == best_dist)
        {
            best_closer_to_player = false;
            best_target           = *ri;
        }
    }
    if (best_dist == INT_MAX || !in_bounds(best_target))
        return (false);
    monster_pathfind mp;
#ifdef WIZARD
    // Remove old highlighted areas to make place for the new ones.
    for (rectangle_iterator ri(1); ri; ++ri)
        env.map(*ri).property &= ~(FPROP_HIGHLIGHT);
#endif
    if (mp.init_pathfind(mon, best_target))
    {
        mon->travel_path = mp.calc_waypoints();
        if (!mon->travel_path.empty())
        {
#ifdef WIZARD
            for (unsigned int i = 0; i < mon->travel_path.size(); i++)
                env.map(mon->travel_path[i]).property |= FPROP_HIGHLIGHT;
#endif
#ifdef DEBUG_PATHFIND
            mprf("Found a path to (%d, %d)", best_target.x, best_target.y);
#endif
            // Okay then, we found a path.  Let's use it!
            mon->target = mon->travel_path[0];
            mon->travel_target = MTRAV_WALL;
            return (true);
        }
    }
    return (false);
}

    }
    if (mons_wall_shielded(mon) && grid_is_solid(mon->pos()))
    {
        // Monster is safe, so it's behaviour can be simplified to fleeing.
        if (mon->behaviour == BEH_CORNERED || mon->behaviour == BEH_PANIC
            || isScared)
        {
            mon->behaviour = BEH_FLEE;
        }

            // XXX: If a monster can move through solid grids, then it
            // should preferentially flee towards the nearest solid grid
            // it can move through.  It will be (mostly) safe as soon as
            // it enters the wall, and even if it isn't, once it moves
            // again it will be on the other side of the wall and likely
            // beyond the reach of the player.

            else if (mons_wall_shielded(mon) && _find_wall_target(mon))
                ; // Wall target found.

    }
    if (mon->travel_target == MTRAV_WALL && grid_is_solid(mon->pos()))
    {
        if (mon->behaviour == BEH_FLEE)
        {
            // Monster is safe, so stay put.
            mon->target.set(mon->pos().x, mon->pos().y);
            mon->foe = MHITNOT;
        }

    if (mons_is_fleeing(monster)

    if (mons_is_fleeing(monster) && monster->travel_target != MTRAV_WALL

    case MONS_ROCK_WORM:

    case MONS_ROCK_WORM:

    case MONS_ROCK_WORM:

    case MONS_ROCK_WORM:

    MTRAV_WALL,        // Earthworms travelling towards a wall.