The speaker admires someone who seems shy and unaware of her appeal. He says her natural appearance and small gestures attract attention, even though she does not recognize this. The feeling is affectionate and excited, with a hint of frustration: he wants her to see herself as he sees her, but the song keeps returning to the idea that she does not know.
โTurning headsโ means making people look because they find someone striking. โLight up my worldโ is a metaphor for bringing happiness or excitement into the speakerโs life. Smiling at the ground and turning away suggest shyness or discomfort with attention, though they do not prove exactly what she feels.
The central twist is that her lack of self-awareness is presented as part of what makes her beautiful. This sounds like a sincere compliment, but it also creates a playful contradiction: the speaker praises her for not knowing she is attractive, rather than asking how she sees herself. The lyrics leave her inner feelings mostly unknown, so her shyness may be charming to the speaker without necessarily meaning she is interested in him.