And easy. For example "futbolista" is "female football player", because it ends in "a", and "futbolista" is "male football player" because... Wait what?

Another easy example is "mar" (sea). It's clearly masculine. Except if you're a poet in love with the sea and you make it female because "no homo" I guess.

OK, the sea is fluid (pun intended), makes sense. What about the computer? "Computadora" is femenine. But it's synonym "ordenador" is masculine. So it's a property of the word, not what it represents. This creates a rare case when someone use the english "desktop" to refer to the computer, but still inherit the female from "computadora", so it's "la desktop".

Or my favorite, Mano (hand), witch is strong so obviously male. But if it's little hand (manita) then it's not strong so female. Except in some counties were remains male.

Next week in "WTF is wrong with Spanish: ser and estar ("to be" and "to be, but like different")

logic or rules come from

That is a "natural" language. Not C++ or Esperanto. No logic. Just bullshit and idiocy.

is it harder than expected for folks who cannot hear the sound?

Absolutely trivial for anyone. If the word ends with "a", it is female. If any consonant -- male, "o" -- neutral.