You should add an Events section for the Idle Game Text Files so you can add events to your game, like the golden cookie in Cookie Clicker. Some of them could happen on certain days of the year, and others could happen randomly like the golden cookie. It could look like this:
Events : *ChristmasPresent -gives 1000 toys (Gives you 1000 of the Toys resource) -named Christmas Present|Christmas Presents -visible -happens 25 december -picture :
*RainingCatDog -boosts all Cat production by 10% (Boosts the number of Cats resource produced by all buildings) -boosts all Dog production by 10% (Boosts the number of Dogs resource produced by all buildings) -named Raining cats and dogs|Raining cats and dogs -visible -happens random -picture :
There could also be Apocalypses, like the Grandmapocalypse in Cookie Clicker. They happen either when you reach a certain number of resources or when you buy a certain upgrade. For example:
Apocalypses : *GoldRush -happens 1000000 Gold (one million of the Gold resource) -named Gold Rush -steals 1 Gold per GoldMiner (Steals one of the Gold resource per second for each Gold Miner building you have.) -changes GoldMiner picture to : (Changes the picture of the Gold Miner, similarly to how the grandmapocalypse changes what the grandmas look like.) -ends 24 hours (The apocalypse ends in 24 hours.) -wait 1 week (After the apocalypse finishes, it is one week before another one is triggered.
*UnionStrike -happens upgrade LowerWages (This apocalypse happens when you buy the upgrade Lower Wages.) -named Union Strike -divides Worker effeciency by 100% (Basically the opposite of an upgrade, this apocalypse reduces the amount of resources the Worker unit can produce.) -changes Worker picture to : -ends upgrade BanUnions (This apocalypse ends when you buy the upgrade Ban Unions.) -wait forever (This apocalypse will never happen again.)