Cube Enthusiast Determines that You’ve Been Shuffling Wrong

Last updated on January 16, 2025

Professor of Symbology | Illustration by Jason Rainville

Shuffling debates have been all the rage in MTG for decades now. The goal of shuffling is of course to fully randomize the cards in front of you. Veteran players have doubtless heard of things like “pile shuffling,” “mana weaving,” and the like, which are infamous for their failures to accomplish true randomization. While most of us can properly randomize a 40-60 card deck, would you be confident in your ability to randomize hundreds of cards at once?

What Was the Discovery?

Strategic Planning | Illustration by Robbie Trevino

Anthony Mattox of Lucky Paper has found the answer after some careful testing with a cube of his. In a recent article titled “The Shuffler Really is Broken: Finding the Best Method for Shuffling Cubes,” he goes through his method in an interesting article that covers how he arrived at his conclusions. He started with the logic of seven riffle shuffles being enough for your average 60 card deck, then worked to apply that to Cube. To summarize his findings:

• The technique Mattox ultimately recommends is called a “broadcast shuffle“, which can efficiently mix large chunks of cards together. To do so:
  • Split your 360+ card Cube into a row of four stacks. You can do more stacks if a quarter is too large to comfortably shuffle.
  • Mash or riffle shuffle each stack as you would a deck, just three times each.
  • Split the first stack into a second row of four. Split the second in quarters and add the quarters to the new row. Repeat with the last stacks until your new row has four stacks, each made from quarters of the previous stacks.
  • Repeat four times, shuffling each stack and “broadcasting” them into a new row.

Broadcast shuffle simulation by Anthony Mattox – Source

Essentially you are riffle shuffling stacks, then splitting them into smaller stacks, mixing those, and repeating several times. While a little time consuming, this produces genuine randomness, which can be challenging with such a large stack of cards (usually 360+). Mattox's article offers visual simulations to track exactly how the method works, and what the randomness looks like using different Cube sizes.

Is Broadcast Shuffling Applicable to Smaller Deck Sizes?

Highspire Artisan | Illustration by Anna Steinbauer

Draftsim reached out to see if this method of shuffle optimization could be applied to smaller deck sizes. According to Mattox: “It's only relevant if you're dealing with a set of cards larger than you can riffle shuffle all at once. Otherwise, the standard heuristic of shuffle seven times still works.” He goes on to say that this method could also work for 99-card Commander decks, which are often just a little too large to riffle shuffle as one whole, as well as lesser-played formats with larger decks, like Battle Box or Forgetful Fish/Dandân.

The author found it largely superfluous with anything smaller than that though, as seven riffles will consistently randomize 40- and 60-card decks.

If you find a detailed examination of randomness interesting, then Mattox's writing (complete with visual diagrams) should be a interest, especially if you're an aspiring or veteran Cube designer. And even if that's not your cup of tea, give the broadcast shuffle a try the next time you cube. Your pod will thank you!