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Comment by darepublic | Hacker News Reader

> Despite being very unlikely to happen during your challenge, the game-ending sequence of S and Z blocks is guaranteed to occur at some point in a long enough game of Tetris.

Thos is probably right but do we know for sure tetris selects the shapes purely at random

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No, that's a common myth that a random sequence will eventually see every possible subsequence.

Easy to construct a sequence of just 1 and 0 thats infinite and not repeating, without having a single 2 nor 3.

But that’s not what’s happening here - the model here is that every piece has a uniform probability of being selected next, in which case every possible subsequence appears in the limit.

While a sequence where one possible subsequence never appears has probability zero in the limit, it’s still a possible random outcome. Incidentally, every concrete infinite sequence has probability zero.

Yes, but "in limit" does not mean "will happen".

E.g. it might be that there will never be "I" piece at all, even for infinite random sequence. Yes, probability of that happening is exactly zero, but that might happen.

For example, if we select at random any number between 0.0 and 1.0 -- probability of selecting it is exactly zero. But we still selected it.

It’s implementation specific. DMG-01 Tetris attempted a weighted random approach but I believe other versions changed the weights and improved the “randomness”.

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