Heads-up
Poker with two players
Definition
Heads-up (HU) is the two-player configuration: a pure face-off where every hand plays against a single range. You meet it at the end of every tournament or Spin & Go, and as a format in its own right (HU cash, HU SNGs). Positions there are peculiar: the button posts the small blind, acts first preflop but last postflop — combining initiative and position, a major structural advantage. Heads-up ranges are the widest in poker: with only one opponent to beat, average hand strength collapses and a hand like K7o, trash in 6-max, becomes a standard button open. Solvers open 70 to 90% of buttons depending on depth. Corollary: relative values change — top pair weak kicker is often a big-pot hand, and relentless aggression is the norm. HU is poker's best laboratory: you can't hide waiting for premiums, every hand is a decision. It's also where reading your opponent's frequencies pays the most: against a player who folds their BB too much, widening the button further is immediate, measurable profit.
Spin & Go endgame, 25bb effective. On the BTN/SB, opening ~80% of hands is standard; K♦7♣, unplayable 6-handed, is a clear open here. Across the table, the BB must defend very wide too — folding 60% of hands to a min-raise would be a direct hemorrhage.