"Je n'ai pas vu les boutons que tu as choisis."

Translation: I didn't see the buttons that you chose.

[HoangHieu4]

What's the difference between "button" and "touche"?

[tachyonashley123]

"Touche" should be understood as "push button". Depending on context, it might also mean "key", as on a piano, keyboard or typewriter.

"Bouton" might refer to a push button, but can also refer to a button of the kind you use to fasten your top.

[LouThompson]

How would French differentiate between "didn't see" and "haven't seen"?

[--Roody--]

I don't know. Maybe Je n'ai pas encore vu.

??? Does anyone have a better idea? Both are the passé composé tense.

[Louradour5]

You wrote (have written ?) an extra "encore" which is not in the original sentence.

[Nathan173901]

They don't. There is no such distinction in many languages, not only in French, which poses some problems when learning English.