Rompecabezas literally translates to "head-breaker", but it's the common Spanish word for "puzzle". It's an engaging word that paints a vivid picture.
In the song, the lyric "Cuando al rompecabezas, no le cuadran las piezas" (When the pieces don't fit the puzzle) uses this word metaphorically to describe a situation where things aren't making sense or fitting together in a relationship, revealing a deeper truth or beauty.
Caramelos de Cianuro's "Yo No Quiero Más Calor" is a passionate declaration of desire and a rejection of anything less than the warmth of a loved one. The singer is feeling lonely and cold, and the only thing that can fix it is being with this person. He sings, "En las noches solitarias, cuando tiemblo de ganas / Es por no despertar a tu lado cada mañana" [In the lonely nights, when I tremble with desire / It's for not waking up beside you every morning].
He makes it clear that this person's presence is all he needs, repeating "Yo no quiero más calor que tu cuerpo ante el mío" [I don't want more warmth than your body against mine]. He even finds beauty in imperfections, noting, "Cuando al rompecabezas, no le cuadran las piezas / Te revela frente a mí tu verdadera belleza" [When the puzzle pieces don't fit / It reveals your true beauty to me]. It's a song about finding ultimate comfort and belonging in another person, even amidst life's challenges and personal struggles.