Game like Descent

Hi all,

In a previous life, I was a big fan of the game Descent. It's a pity it
never made the jump to MacOSX, and although there were some community
efforts for to get it ported, they were all fairly unstable - and Descent 3
was never ported, so had to run in Classic, which lead to it's own
problems...

Anyway, I got a suddent urge to play descent again after a few years, so I
was just wondering if anybody could recommend a game like Descent for
MacOSX. I know there are plenty of flight sims out there, but are there
first-person 3d shoot-em-ups, set in tunnels & tubes, that would be
comparible to Descent in gameplay?

Thanks,

Tim