In a heads up game, the dealer is also the small blind. Because of this, when the game goes from three to two players or from two to three players, separate rules apply in order to accommodate for the dealer and blinds rotation. I've seen the button moving once, twice or not moving at all. Can anyone explain when and what happens in each of the situations?
And a quote that caught my attention:
When there are only two players
The normal rules for positioning the blinds do not apply when there are only two players at the table. The player on the button is always due the small blind, and the other player must pay the big blind. The player on the button is therefore the first to act before the flop, but last to act for all remaining betting rounds. A special rule is also applied for placement of the button whenever the size of the table shrinks to two players. If three or more players are involved in a hand, and at the conclusion of the hand one or more players have busted out such that only two players remain for the next hand, the position of the button may need to be adjusted to begin heads-up play. The big blind always continues moving, and then the button is positioned accordingly. For example, in a three-handed game, Alice is the button, Bob is the small blind, and Carol is the big blind. If Alice busts out, the next hand Bob will be the big blind, and the button will skip past Bob and move to Carol. On the other hand, if Carol busts out, Alice will be the big blind, Bob will get the button and will have to pay the small blind for the second hand in a row.