Kan strategy
Kan is a naturally risky action, due to the nature of kandora. When a player calls kan, any player - including the kan-declarer's opponents - may benefit from the kandora. Therefore, some assessment should be made when calling kan.
Offense
Under most circumstances, the call for kan is an offensive move. The player gets an extra draw from the rinshanpai and chances for the kandora. If the hand is tenpai, then the hand has a chance for rinshan kaihou.
If a kan-declaring player wins, then their opponents will never get a chance to benefit from kan dora. Therefore, if a player believes that they are likely to win (e.g. reaching tenpai early, or iishanten very early), then kan may be advised.
Riichi
A call for kan reveals kan dora. Any player who has declared riichi will also benefit from kan ura dora. Therefore, a player in riichi will often call kan if it is possible. First, it reveals two extra dora instead of the usual one. Second, a player in riichi is already in tenpai; thus, they are more likely to win. Conversely, opponents should be wary about calling kan when another player is in riichi for the same reasons.
When playing with real tiles, players must always be aware of whether a kan call can legally be called. Players using game software or online platforms do not need to be aware because the programs handle the situations for them.
Defense
A player in betaori (full folding) should usually avoid declaring kan, because it removes four discard options from your hand, and may increase the opponent's score. For shouminkan/kakan, there is an added risk of chankan.
Players can apply kabe if an opponent calls kan. If all four tiles are visible, e.g. from an opponent's kan call, then it will make certain types of wait impossible. For example, If a kan of 3 is called, then the wait patterns of 23, 34, and 13 of the same suit are impossible. Thus, 1 and 4 become safer. If all four tiles are in your own hand, then there's no need to actually call kan in order to benefit from kabe.
Shifting the draw
When kan is called, one tile from the live wall shifts over to the dead wall. With this mechanic, players can call kan to deny players ippatsu or the haitei draw.
Call timing
Kan is not mandatory, so players do not have to call kan immediately. Instead, they can keep the fourth tile in their hand, declaring kan if/when appropriate. However, delaying a kan will reduce tile efficiency, if the extra tile is not connected to another tile in the hand.
External links
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