Improve the regular (tunnel) cave type

While the inclusion of noise caves definitely made caves more interesting. The old cave type which I'll call tunnels is still there and are still kind of boring. I would like the tunnel caves to vary more in shape and size. These caves should also spread more and intersect more with other tunnels and other cave types. However, these caves should remain being closed and compact to contrast them from the open noise caves. This would make caves more explorative.