Is this Akinator for video games?
Close. Akinator guesses characters; Töllö guesses games. You think of a game, it asks yes-or-no questions about where you played it, what you did in it and what it looked like, and it guesses, usually in under twenty.
How does it know so many games?
Every game in its head has an answer to every question it can ask, written ahead of time. After each of your answers it weighs every game at once, asks whatever splits the rest best, and guesses when one game stands clear.
What if I answer something wrong?
It copes. No single answer rules a game out, it only makes it less likely, so a misremembered detail or two still leaves your game in the running.
Which games can it guess?
Thousands, on PC and every console from the arcade days on, weighted toward the games people actually think of first. If you stump it, tell it what you had in mind: stumps are how it learns what to add.
What does it keep?
Your answers and the game at the end, with no account and nothing that says who you are. That is how its answers get checked against real players'.