Our toilet broke.
It's pretty trivial to replace any part inside the tank of a toilet. Everything is a standard size, and last time I checked there wasn't a whole lot of variation between the different brands of replacement parts. Apparently toilet parts have developed a lot more "features" since then.
We ended up getting a super-quiet fill valve and a mod kit for transforming our toilet into a two-button Euro-flush technotoilet. This is the anatomy of a normal American toilet:
We like making things more complicated than necessary, so this is the anatomy of our toilet now. We're not completely sure how the flapper thingy works yet, but so far it does what it says it does.