Birthday by Katy Perry is in C at 126 beats per minute and runs 3:30 across 57 bars. It uses 10 chords — Fmaj9, Dm7, C, F, Dm, Am, Fmaj7, Dm9, and a few more. The chord diagram changes as the song plays and the words light up as they are sung, so you can strum and sing along without reading ahead.
Want the melody line note by note? Birthday guitar melody tab.