For each word, pick the preposition it takes in the locative. Two choices: u (in/inside) or na (on/at). The 200-word deck is reshuffled every time you load or restart, so the order is never the same twice.
Classic traps to watch: u školi (school) but na fakultetu / univerzitetu (university); u gradu (city) but na selu (countryside); u knjizi (book) but na stranici (page). Learn each phrase — the gloss on the card pins down the intended sense.