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How to mash shuffle honestly and straight-forwardly

To mash shuffle a deck of cards is to divide the deck in two halves and mash the two halves together.

Topologically it’s the same as a traditional “riffle shuffle” but instead of riffling through the cards, you just mash them together.

Setting aside how bad card sleeves are for the environment, card sleeves make it harder to riffle shuffle but easier to mash shuffle.

Here is how to mash shuffle in an honest and random way.

Shuffling form

The Elevator

For example, let’s say you have this permutation:

A A A A A b b b b b

You take the bottom half and mash it together with a tiny offset so that the new top card of the combined pile came from the middle:

b b A b A b b A A A

The offset should be minimal. If you make the offset too big, mash more than seven times to compensate.

The “more random part” is the middle part of the deck.

In this example, the B B at the top isn’t particularly mashed up, nor is the A A A at the bottom.

Then, you repeat:

B B A B A b b a a a →
b b B a B a A a B A

B B B A B a a a b a →
a a B a B b B a A B


All the entropy and randomness lives in that middle, mashed up, part. So everytime you re-mash, the top of the deck should come from the middle, mashed-up part. The sum of the two less random “offsets” at the top and bottom need to be much smaller than the random “elevator” in the middle. The “elevator” has the randomness that you want to spread into the rest of the deck as much as possible. Sort of like when stirring cinnamon into a dough.

If you have shuffled your opponent’s deck (which means you’re the last person who’ll get to shuffle it) also cut the deck.