Race to five in a row, but flank an enemy pair and you snatch it, banking captured stones as indestructible anchors that change the whole board.
Players take turns placing stones on the intersections of the board; Black moves first. You win the instant you make five of your stones in an unbroken row, column, or diagonal, or by capturing five enemy pairs.
Capturing is custodial: when your two stones bracket exactly two of the opponent's stones in a line (you–enemy–enemy–you), that pair is captured and removed. Each captured stone banks to your hand as anchor ammo, which you can spend to drop an indestructible anchor stone that can never be captured.
Five in a row plus custodial capture — bracket exactly two enemy stones and take the pair, five pairs wins — is Pente, created in 1977 by Gary Gabrel, which added capture to the pure line-making of Gomoku.
The original addition is that captured stones do not simply leave. They bank to your hand as anchor ammunition to spend later.
Pente's capture rule already changed the calculus of line games: a four you cannot defend is worth less than a pair you can take. Making the captures reusable pushes that further, because a capture is now both a subtraction from the opponent and a deposit for yourself.
Fivelock blends the five-in-a-row connection genre with custodial pair captures and an original anchor-banking twist, so the board is won by lines and by tactics. This is an original, free browser version with computer, two-player, and online play, ready instantly with no download or sign-up.