In every game, usually speedruns are about killing/destroying. But Terraria is also about building. So I though, building something would be a refreshing and interesting type of category.
The closest I can recall is house% in Minecraft, but I think there are a lot more interesting things.
The hard part is finding and standardising buildings for runs.
Some of my ideas;
pyramid or some kind of cultist building
house in every biome%
castle/mansion with specific furniture,etc
functioning real life house(electricity, bathrooms,etc)
So the runs would include collecting specific blocks, the building itself and usually some bossfights.
Im surprised that apparently there is no For the Worthy, master (legendary) category, as it is probably the hardest possible. (I guess hardcore would be too extreme). Yet on youtube/twitch there are already runs.
Sorry if I am just blind and I missed it.