Learn Spanish (Latin America): Nosotros inventábamos reglas tontas para el juego. - We used to invent silly rules for the game.

inventábamos is in the imperfect tense. We use the imperfect to talk about past habits or things we used to do repeatedly. If we used the preterite (simple past) tense inventamos, it would mean "we invented" (just once, as a completed event). Translating it as "we used to invent" perfectly captures this ongoing habit!

Why is there an accent mark on inventábamos?

In the imperfect tense, the nosotros (we) form of all -ar verbs has an accent mark on the a right before the -bamos ending. This tells you to put the speaking stress on that exact syllable: in-ven-tá-ba-mos. The other imperfect forms of this verb (like inventaba or inventaban) do not need this accent mark.

Why does the adjective tontas come after the noun reglas?

In Spanish, descriptive adjectives like tontas (silly) almost always go after the noun they describe. Also, because reglas (rules) is feminine and plural, the adjective changes its ending to match, going from the default tonto to tontas.

Why do we use para instead of por to mean "for" here?