"O.O" is a song recorded by South Korean girl group Nmixx for their debut single album Ad Mare.
[7] "O.O" was written by Dr.JO (153/Joombas), composed by EJAE along with Brian U, Enan, MarkAlong, Charlotte Wilson, Chanti, Awry, Ayushy, Jan Baars, and Rajan Muse from The Hub, and arranged by the former three.
She stated that "'O.O' comes off as a weak facsimile in the face of the complexity" compared to aforementioned songs as "'O.O' tries, but fails, to capture any attention for very long.
"[12] Korea JoongAng Daily noted that "Because of its disjointed nature, many criticize that the song tries to push for an edgy and provocative image but is difficult to follow as it lacks a basic musical structure."
Korean Music Awards selection committee member Jung Min-jae said that "I don't think 'O.O' would be seeing [negative] reactions if the song was catchy, no matter how convoluted."
[11] In a more favorable review, on the other hand, Divyansha Dongre of Rolling Stone India described "'O.O' as a quintessential K-pop track [which] meshes multiple genres into one".
Divyansha noted that "the switching between soundscapes may get slightly overwhelming for some listeners [due to the song] opening [which] is a powerful mix of trap and bass-synth [while] its second verse sees the soundscape quickly adopt the vibrancy and zest that pop rock has to offer".
Overall, Divyansha stated that "[the song] serves as a fair introduction to the caliber and talent Nmixx members have to offer".