A lot of options that affect gameplay can be changed in OpenTTD. Many of these options can be changed from the Advanced Settings window, but for some of them you have to edit the config file, openttd.cfg. Most advanced settings improve gameplay or the interface, while others give you more power in the game.
Changing Advanced Settings
The Advanced Settings window allows you to change most of the available settings from within the game. The Advanced Settings window has a tree-like structure, divided up into the following main sections:
Buttons are green to show the setting is on, red to show it is off. Arrow buttons change the value of the setting like a horizontal scrollbox. Clicking on a patch-line with arrow buttons shown will bring up an edit box, where the desired value can be typed in.
There are three "levels" of settings, the *basic*, the *intermediate* and the *expert* level, which each successively adds more settings to the game which in turn need a deeper understanding of how they affect gameplay.
Changing settings in a running game
If you access advanced settings from the main menu, that affects new games only. If you want to change advanced settings of a running game, load it first and then change the settings you want to change.
HistorySome features that have been advanced settings (patches) in older versions of OpenTTD can now be found under game options or cheats. Some of them might even have become permanent features that you cannot disable.
Prior to r14275, the "Advanced Settings" were called Patches. This was dropped in favour of "Advanced Settings" in order to avoid confusion with TTDPatch in general, or patches (in the technical sense) against the source code of OpenTTD often found in the Development section of tt-forums.
Since r14974 the tabs at the top of the window are removed and all advanced settings are listed in a tree structure. This allows for subcategories that can be expanded and collapsed independently. The former tabs (Interface, Construction, Vehicles, Stations, Economy and Competitors) are now top level categories and they can now have subcategories, for example the subcategory Trains in Vehicles.