What Does “APT. (feat. Bruno Mars)” Mean?

"APT." is named after a popular Korean drinking game (아파트, "apartment") and was co-written with Bruno Mars. The playful, upbeat track uses the game as a metaphor for the ups and downs of a flirtatious relationship. The song became a massive global hit, reaching the top 5 on the Billboard Hot 100 and spawning a viral dance trend.