I could not agree more with isidoro. I also want a more challenging game*. Without the main connection rule it would be too tempting to cheat and delete connections between cities to force users to take my trains 🙂
However, there is a difference between a hard game because it is well designed (rewarding good play and punishing mistakes) and a game that is hard because it badly coded. There are many times that I just want to replace a curvy road with a straight one or upgrade a small track to a larger track … With the main connection I must try over and over again to make detours and (sometimes they are not recognized as such even if they are short) then bulldoze the old line, replace the old track and hope I can bulldoze the detour (which has become a new main connection)… It is really a huge pain.
It would be much better if the game lets you bulldoze anything but charges you the cost of rebuilding the missing main connections. Even better, it would be if the game lets you enter some “building/planning” mode, build anything with the right to undo the different parts and then commit to the whole construction before reentering the “playing mode”.
* Suggestion to developers. I think that even hard is somewhat too easy that you must even not really pay attention to optimize anything and still make a lot of money. Because of that I lost most of the interest in the game since all plays are somewhat similar. I though I might try to modify the game – if possible – to increase maintenance costs of infrastructure like rail, road, stations, depots and probably even trucks. However to really bring some more replayability there should be:
1) more map diversity ( come on, developers, it should not be that hard to do and has been requested by several players … e.g. rectangular maps, cities and industries far apart, coastlines etc.)
2) some preconfigured maps ( I would love to connect regions or even better countries like Switzerland, France, England, Europe … just make some abstraction of the scale of the maps, put cities farther away from each other and slow the passing of time)
3) some maps with some quality objectives or scenarios (e.g. reach a really high coverage in certain areas, or implement a certain mix of transportation modes, connect certain cities or industries …)
4) bring more dynamism in maps, e.g. by spawning new industries over time (maybe complexifying the industry chains over time) and delete the most obsolete ones
5) competitors or other players to beat ( I know it will never be implemented in train fever, but I have hopes for your next game ).