OSTER project's Twitter

As I said, mahjong tiles are like cards. And there are tiles that, like cards, have a suit akin to hearts or spades and a number, but there are also tiles that aren't like that with characters written on them.

Regarding the ones that have card-like suits, there are three suits in mahjong. They're called manzu, pinzu, and sozu, but whether you remember the names or not, you're fine if you can just recognize the suits. Each of these numbered suits goes from 1 to 9, and there are four copies of each tile.

Mahjong is a game about combining these guys skillfully to make kinda nice-looking patterns, and whoever is able to make those combinations in the form "three, three, three, three, two" basically wins. These combinations of three tiles are called "mentsu." And the combination of two tiles is called a "jantou."

A mentsu can be formed either with a "run," like 1-2-3 or 5-6-7 in the same suit, or with "three of a kind" like 4-4-4 or 6-6-6 in the same suit. On the other hand, jantou can only be formed with "two of a kind," like 8-8 or 7-7; "runs" like 1-2 or 5-6 won't work.

For example, say we have a hand like this. (Manzu 1-2-3, manzu 3-4-5, pinzu 1-1-1, sozu 7-8-9, chun-chun) From left to right, it makes a run, a run, three of a kind, a run, and two of a kind. If you make something that looks like this, that's agari (victory). Thus, the objective is for players to aim for this formation as they repeatedly take and discard tiles.

With that in mind, suppose that the moment you discard an unwanted tile where everyone can see, one of the other players says this. "Ahh, if I had that tile you just discarded, I could make a mentsu. I'll take that tile." What does that mean? Basically, there's a system where if a player could use a tile someone discards to create a mentsu with their tiles, they can declare "I'll take that tile."

The "I'll take that tile" system has two versions: either "I'll take that tile to make a three-of-a-kind mentsu," or "I'll take that tile to make a run mentsu." Declaring "I'll take that tile to make a three-of-a-kind mentsu" is called "pong." Furthermore, declaring "I'll take that tile to make a run mentsu" is called "chi."

Statistically, it's harder to make three-of-a-kind than it is to make a run, so while pong allows you to take a tile from anyone, chi only lets you take from the person to your left. Regardless, these moves that let you take tiles from others to create mentsu are quite powerful, so there are penalties of sorts for using them.

One of them is that you must reveal to everyone "this is the mentsu I completed by taking this tile!" Doing this gives the other players hints about what sorts of tiles you have; also, even if you look at your tiles and decide you want to change your mentsu combinations, you can no longer mess with or take tiles from revealed combinations.

Now, let's get back to the conditions for agari. At the start, I said that whoever assembles four mentsu and one jantou first wins, but there's actually another condition. I can already hear the people saying "you should've said that to start with!", but what you absolutely need to achieve agari are yaku.

"Yaku" refers to assembling tiles in a specific combination, much like a flush or a straight in poker. There are a variety of yaku in mahjong, and if you don't create at least one such yaku, then even if you assemble the formation for agari, you cannot call agari. (Yaku-less)

The most major and unique of these yaku is riichi. The yaku "riichi" is actually not related to combinations such as "everything in the same suit" at all, so it's a rather special case. The requirement for riichi is to never once use the "I'll take that tile" system, and arrive at a state of "I'm one tile from achieving agari" on your own power. This act of declaring to everyone "I'm one tile away from agari" is the "riichi" yaku.

If you aren't taking tiles from others, just drawing and discarding tiles all on your own, it takes considerable luck to create four mentsu and one jantou, so riichi is a sort of "achievement award" yaku. ("Good effort") In other words, the moment you use the "I'll take that tile" system even once, you forever lose access to the riichi yaku. ("See ya") So if you casually say "I'll take that tile" without considering how to create any other yaku, this can result in a tragedy where even though you completed the agari form, you can't win because you have no yaku.

There are also a few other yaku besides riichi that become impossible to achieve if you use the "I'll take that tile" system. This is why it's recommended that beginners try to avoid using the "I'll take that tile" system.

So far, we've focused entirely on the tiles with numbers, but let's introduce the tiles with characters too. First of all, there's the tiles with "north," "south," "east," and "west" on them (北南東西, in blue), then one that's kinda just all white (haku), one that says "hatsu" (發, in green), and one that says "chun" (中, in red) - for a total of seven.

The tiles with characters, unlike the tiles with numbers, have no concept of "runs," so you can only create a mentsu by assembling three of a kind. There only exist four copies of each character tile as well, making assembling three of a kind very difficult. Thus, when it comes to haku/hatsu/chun, simply having three of a kind grants you a yaku called "yakuhai," satisfying the conditions for agari. You're even allowed to use the "I'll take that tile" system to assemble them, so it's a convenient yaku.

Regarding the north/south/east/west tiles, their value changes depending on the time and place. Tiles that either match the direction written on your side of the table, or the direction given by the thing that says "east is favored" or whatever [here displayed in the center of the table], are treated as a yaku if you assemble three of them.

So then, whether by taking tiles from others or slowly assembling things on your own, suppose you get to the point of "I'm one tile away from agari." In this position, if you find that "If I took that tile you just discarded, I'd have agari! Gimme!", there's a system that lets you shout "ron!" to take that tile and achieve agari. When someone says "ron!" to achieve agari, the person who had "ron!" said to them must give points to the winner.

Suddenly, we've introduced the concept of points. The way it works is that each player starts with some points, and the first person to reach agari takes points from the other players. There are numerous matches like this, and when it's all over, the person with the most points is the overall winner.

Thus, all players must be fearful whenever they discard a tile, asking themselves who is one tile away from agari, and which tiles might lead someone to shout "ron!" - a rather stressful mindset. Even so, there are conditions for this ron agari as well: you are forbidden from taking a tile for ron that you have discarded earlier in the game.

When you discard tiles, you put them in the "Unwanted Tile Discard Corner," but each player has their own separate discard corner. This means that when someone's giving off an aura of being near agari, as long as you're discarding a tile that player has discarded before, there's no worry of them shouting "ron!" and taking it.

In this way, the player best able to observe other people's expressions and forestall them to achieve agari first wins - such is the dark game known as mahjong.

Also, the information you can gleam from the "Unwanted Tile Discard Corners" is rather important. For instance, suppose there's a tile you're after, one that would be helpful if it showed up. However, there are only four of each tile, so between the "Unwanted Tile Discard Corners" and the tiles revealed as part of the "I'll take that tile" system, once all four of the tile you want show up, you've lost any chance of coming upon that tile yourself. At that point, you must give up on the tile you wanted and change course to create different combinations, so it's quite despair-inducing if this occurs late in the game.

By the way, in card games like poker, numbers have a "strength" (i.e. a 3 is weaker than a King) resulting in things like the same hand being stronger if it uses larger numbers, but no such concept exists in mahjong's case. (1 and 9: equal) That said, there are things that are statistically easier or harder to assemble. What do I mean by that? For instance, consider what mentsu can be made using the number 5. The runs 3-4-5, 4-5-6, 5-6-7, and the three-of-a-kind 5-5-5. So you can consider it as being usable for four possible combinations.

However, if you consider the number 2, you only have 1-2-3, 2-3-4, or 2-2-2 - three possibilities. In the case of 1, there's 1-2-3 or 1-1-1 - only two. In other words, in mahjong, numbers are statistically harder to make mentsu with the closer they are to the edges (1, 2, 8, 9), while the numbers in the middle, 3 to 7, offer more opportunities. There are even yaku that, taking this statistical difference into account, involve mentsu containing 1 or 9, so deciding what yaku to pursue based on the tiles you're dealt at the start is part of the fun.

Also, deciding how to go about combining the tiles you have to make mentsu is actually rather difficult as well. For instance, say you have the tiles 6-6-6-7-8-9 in the same suit. In this case, you could make the two mentsu 6-6-6 and 7-8-9, or you could be daring and discard the 9 to go with 6-6 and 6-7-8, a jantou and a mentsu. How you should combine the tiles you draw to get closer to agari, and to increase your odds of victory - having the ability to ad-lib and flexibly rethink your combinations is rather crucial.

So, that was a simple explanation of mahjong's rules. But there are also numerous other in-depth rules like "dora," tiles that give bonus points if you get agari with them, and "kong," which you can declare by collecting four of the same tile. So please look them up if you're interested.

This ends my explanation of mahjong for people who know absolutely nothing about it. Well then, goodbye.