This is an .sol file which has made no progress on the Bridge Building minigame. It is for your convenience, you need not use this exact file, but you must use one that also has no progress on this minigame or reset to a state with no progress on the minigame in order for the run to be valid. Note that this is not an .swf file, as .swf files themselves do not store save data. You should place the .sol file according to this guide, probably after making a copy of the swf file you use to play the game (allows you to maintain different saves more easily).