The game starts with four privates and two Director's Certificates
available. There are eight major companies total, which come out in
pairs; the four privates can each be exchanged for a share in the
first four major companies (which are reserved for those privates as
long as they exist; it's not "use it or lose it" initially).

There's six auctions for the right to buy one of these six things (ie,
when you win the auction you take whichever you wanted).

There's a fifth private that comes out with the 6 trains. When it's
bought, the other 4 privates evaporate if they're still around.

When the first 9 train is bought there's an endgame procedure where
first the Southern Railway buys everything and stops construction, and
then BR forms and closes the two least profitable railways each OR, so
I guess it's really good to have the best company then because you'll
get to run it more often.

Stock sales are half price for trainless companies. There's no
requirement for there to be a Director. It's a "zig-zag" stock market
which effectively makes payout/withhold jumps twice as much as stock
sale penalties, and companies with very high or low prices don't take
a penalty on the first cert sold. The cert limit goes away when the
first 8 train is bought.

You float when 50% of the IPO is sold. If your start hex has no track,
you immediately lay a tile (and this doesn't use up your first OR's
build). It's full capitalisation, but company money is separate
"company credits" so can't break the bank.

Trains are N+M, which means they can run to up to N+M stops, N of
which can be large stations. I think there is a vicious train rush
after the brown tiles are out.

Village dots can become small stations or "halts". Halts pay subsidy
to the company, not revenue to divide. Either of these can be bypassed
by a train (not counted or scored) to visit more large stations (up to
"N"); large stations can't be bypassed.

You lay up to two yellows or do one upgrade. If you lay two yellows
neither can be a large station.

Upgrades need you to be able to reach the tile (and either some of the
additional track or improve the value of a hypothetical route) _with a
train you actually own_, ie, that can reach far enough. Hence a
company without a train can do no upgrades.

Routes are pretty normal except you can pass though one tokened-out
station with one train and that, 1862-style, your routes have to form
a single network meeting at stations (of any size).

You can quadruple-jump on a payout.

You can't buy another company's only train unless you yourself are
trainless.

You must have a train if you can. If you don't, and do have a route,
you are insolvent - you can't place tokens, can't upgrade track, can't
pay construction costs, must withhold, and must buy a train if it can
from the bank. When you run you "lease" the smallest bank train which
runs as an N+0 and pays £40 plus £20 for each station or halt. How
complicated.

A company with no Director can't build, runs for maximum revenue, and
withholds.

The endgame procedure is lengthy and in the rulebook.

Bankrupt companies (price reaches zero) keep their treasury, trains,
and tokens, and can be refloated in a fresh IPO (getting a fresh round
of capitalisation and their treasuries). The existing shareholders
lose everything at bankruptcy.