This is a list of things I'm regularly asked to do, but which are either impossible to do, or at least an awful lot of work:
- Diagonal bridges or tunnels. Complication: TTD has no provision to store a straight track, nor can the graphics engine display them. same for the pathfinding, it always thinks a straight track is under and on the bridge
- More stations or more depots. Both stations and depots have an ID value that is stored in a single byte in memory. Because of this, the IDs can only go up to 255, allowing at most 256 stations or depots. For stations, a couple of the ID values have special meanings, so that only 250 stations are possible. However, because they are stored in a byte, it is not possible to have more stations or depots than 255. It is all but impossible to change the ID to use a word value, which would be required to do that.
- Joining more than one of each station facility type in a single station, e.g. two joined bus stations. While it is theoretically possible to place those on the map, the internal station structure can only hold the position of one of each facility type. Therefore the vehicles would only use one of them as well. In addition this would eventually turn into a ghost station.
- Larger airports (more runways). It's possible, but would involve recoding the whole aircraft movement scheme of an airport, which not much is known about. This may be possible, but requires more time and effort than any patch developer is willing to spend at the moment.
- Larger maps. This is all but impossible, because the whole program assumes a coordinate has 8 bits for each direction, totalling a 256x256 grid. One would need to change thousands of places that store 8 bit coordinates, which is just not feasible.
- A patch for the original Transport Tycoon. I have worked on TTDPatch for almost six years now, and asking me to duplicate that work for TT original is just a little bit unreasonable.