I noticed you straight away when you walked in.
ti o no-TA-to su-BI-to kwan-DO sei en-TRA-to — stress on 'ta-', 'bi-', 'do', 'tra-'. 'Subito' is three syllables: SU-bi-to.
At a social event — confessing that you noticed someone the moment they arrived. A sincere and specific expression of attraction.
'Ti ho notato/a' = I noticed you (passato prossimo). 'Subito' = immediately. 'Quando sei entrato/a' = when you walked in/entered. The specificity of the moment — the entrance — makes it vivid and genuine rather than a vague compliment.
Sei la prima persona che ho visto entrare e non ho smesso di guardarti.
You were the first person I saw walk in and I didn't stop watching you.
Extended version — the gaze continued from first moment
Non si può non notarti.
It's impossible not to notice you.
Says the noticing was inevitable — not a choice but a necessity
Ho aspettato il momento giusto per avvicinarmi.
I waited for the right moment to approach you.
Reveals conscious intention — you were watching and planning
The gathering of courage ('raccogliere il coraggio') before approaching someone is a universally relatable experience. In Italy, admitting it openly is considered charming rather than weak — it shows emotional honesty and that the other person is worth the effort of overcoming shyness.