Some levels can not be solved in a completely "clean" way. For these levels, the bridges which meet most "cleanness" conditions are considered "clean". Everything less "clean" is considered "dirty".
1. The list is divided into two categories:
- "Clean": The bridges have to be as realistic as possible, i.e.:
- The bridge only may have contact with the ground at the anchor points (except on levels that can't be solved otherwise, on those minimal ground contact is allowed, only above the rail level, if possible
- The bridge has to stay undamaged after the train passes
- The bridge doesn't have to stop swinging at the beginning; it works if the train is started immediately as well as with any amount of delay
- The train may not "fly" (it has to stay on the ground or the rails all the time)
- The train may not touch the water surface (except on levels where the rails level equals the water level)
- The train must reach the target in one piece (all cars together) (yes, you can trick the game sometimes...)
- The beams may not penetrate the terrain in edit mode
- "Dirty": No restrictions, the only condition is: the "Next Level" message has to pop up!
2. A "clean" bridge is obviously better than a "dirty" one. Thus, only bridges that are cheaper than the best "clean" bridge are listed in the "dirty" category.
3. For each level, the three cheapest bridges are listed. As an exception, sometimes several bridges can be ranked the same, if they are added on the same update and/or are substantially different.
4. This page is about the cheapest bridges, not the best-looking/funniest/stupidest ones. Such bridges can be found in the Bridges section.
5. A new bridge that isn't cheaper than the current record for the given level won't make it to the list (everyone can look at a bridge and then build a more expensive one) unless it is substantially different than all the other ones. Here, I try to be as fair as possible. So make sure your bridge really should be on the list before submitting it.
6. IMPORTANT: If you modified someone else's bridge instead of building a new one from scratch, please mention this in your e-mail.