f(x) came back with 4 Walls and cemented itself as the group that routinely shits on every other group when it makes a comeback.
I was worried about this comeback. I thought Red Light would end up being f(x)'s magnum opus, and that any track/album to come after it would be a huge disappointment. I also didn't know how much effort SM would put into f(x) with all of the disbandment rumors cropping up due to Krystal and Victoria's contracts expiring in the near future.
Luckily, f(x) took a turn for the better and went with a completely different sound for this comeback. As opposed to the high-energy title tracks of Red Light, Rum Pum Pum and Electric Shock, f(x) went with a mellower, yet still addictive deep house tune. Many might welcome this change from the eccentric structures that Electric Shock and Red Light had.
Also, I could see how people could construe f(x)'s change in sound as a result of Sulli leaving:
"4 Walls sounds much more mature than anything f(x) has done. That makes sense since the most immature member left to scissor her boyfriend's micropenis."
"The music doesn't overpower the vocals anymore because Sulli's shitty singing isn't there to ruin songs anymore."
"I bet Adrian wanted mellower music so that she could peg her fellow members with more appropriate music."
If this happens to me f(x)'s last title track (and I doubt it, as the members get 11 months out of the year for solo work anyway), 4 Walls would be an extremely good track to end their career with.
Anyway, while 4 Walls is a great track, Papi should have been the title track.