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Mathsy card game 21X is blackjack plus algebra, and my head already hurts

But Y?

Blackjack is a playing card game staple. It’s fast and easy, as players simply choose to twist or stick as they draw cards to get as close to 21 without going over. What could it possibly be missing? Well, how about algebra?

Designer Leo Samson and new card game 21X seems to think that’s the case, introducing a mathematical twist (ha, ha) to the classic game of 21.

Like standard blackjack, 21X is played with a single deck of playing cards. Except these cards can’t exactly be called “standard”, because in place of suits and numbers they have algebraic equations. You know, like the stuff you don’t remember from your school maths lessons - 6-4X, 24/X and so on.

The rules are otherwise the same as standard blackjack: players can choose to draw an extra card from the top of the deck, or stick on what they have if they feel it’s close enough to 21. The only complication is that you’ll need to work out exactly what you’re holding by using a number as X - which must be the same across all the cards, and can be a negative number - and solving the equations to calculate your current total.

Some of the highlights from this year's Essen Spiel conventionWatch on YouTube

Every card you draw has the potential to make things even more complicated, as a second factor of N is equal to the number of cards drawn by the player so far. (2 if you have two cards, 3 if you have three and so on.) So instead of a Queen, 6 and 4, you might be holding -2NX, 2X-2X or even X to the power of N. (The cards span easy, medium and hard difficulties, so you can adjust to make it less maths-heavy.)

The player can change X as necessary to adjust to each new card they draw, looking to land bang on 21 (or as close as possible) when they explain their sums. Once a player is close or on target, they can announce it to the group, locking in their X value and giving everyone one minute to make their final twists before seeing who got closest. A solo player can play alone by drawing cards and aiming for 21, if you're just looking to brush up on your mental maths.

According to publisher Naylor Games, which plans to launch a crowdfunding campaign for the "affordable" deck of cards "soon", 21X can be learned in under a minute and played in five - although that doesn’t account for 20 minutes of umm-ing and err-ing as all maths knowledge empties your head, if our experience playing at this year's board game convention Essen Spiel was anything to go by.

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