as the obsolescence of older trains, the availability of different sets of tiles, increased valuation of certain non-tiled cities, closure of private companies, and the ability to merge corporations or form them at higher valuations. Game end is usually determined when the bank runs out of money, and also by player bankruptcy (when a player cannot pay the debt of a company they control). Some games do not end when a player goes bankrupt, while others add other conditions for ending the game such as when a stock reaches a certain value on the stock market, or the most advanced type of train has been purchased. Other games do not feature bankruptcy at all, and enable a player to place a moribund company in "receivership", or be incorporated into a government railway, and walk away from debts. Differences While adhering to common similarities (see preceding section), each 18XX game differs from the others in subtle or significant ways in rule set as well as game map. As with games in general, each individual mechanic has probably been used before, but a new game can put together a set of mechanics which provide a new and interesting challenge. Some typical areas of difference are: Initial Auction – there are many different ways to distribute initial private companies and starting major corporations. Private Companies – most 18XX games have private companies which are entirely owned by one player, and represent the earliest companies in the game and/or provide special abilities. "Privates", as they are called, generally do little other than provide revenue, but in some games they control access to or enhance the revenue of certain hexes on the map. Some games have very similar private companies, some have very different private companies, and some dispense with having private companies at all. Some titles (e.g., 1835 and 1861) also have Minor Companies, which are again owned entirely by one player but play a more dynamic role than Privates. Corporation Funding – some games have full funding for a corporation as soon as it floats, while others have the company receiving money only as each share is sold. Some games require the corporation to reach a historically relevant destination in order to receive some of its capital or earn the best level of income. Company Types – some games have multiple company types. These types may vary based on how many shares are