Same puzzle, same clock, one opponent. The fastest correct solve wins.
Pick a difficulty and a time control, then join the queue. Matchmaking looks for an opponent within 200 rating points of you; if nobody suitable appears within 60 seconds the search times out and you can try again or widen your options.
When a match is found, both players get a five-second preview of the grid before the clock starts — enough to scan the board so the opening seconds are not simply a test of who loaded faster. From there it is a straight race on an identical puzzle.
Duels run at 5, 10, 15, 20 or 25 minutes. The short controls turn Easy and Medium grids into a genuine sprint where scanning speed decides it; the longer ones give Hard puzzles room for the deeper techniques to matter. Fifteen minutes is the default and the most common choice.
The clock does not pause, and the standard competitive restrictions apply: no undo or redo, no candidate display, no check-cell or check-puzzle, and the solver will not touch a puzzle that is live in a duel.
Duels are rated, and the swing accounts for the margin — edging an opponent by three seconds does not move your rating the way a decisive win does. Guests can duel freely, but guest matches are unrated. See Rankings for how the rating and its seven tiers work.
A heartbeat runs during the match so a genuine disconnect is detected rather than being scored as a loss for someone whose browser tab was throttled; the threshold is deliberately generous at two minutes. When a duel ends you can offer a rematch and go straight into another game against the same opponent.
The queue pairs you with an opponent within 200 rating points at your chosen difficulty and time control. If no match is found in 60 seconds, the search times out.
Yes. Both players solve an identical grid on an identical clock, with a five-second preview before the timer starts.
Five: 5, 10, 15, 20 and 25 minutes. Fifteen minutes is the default.
Yes, but guest duels are unrated and do not appear on the global leaderboard.
A heartbeat detects genuine disconnections. The threshold is two minutes, which is deliberately generous so a throttled browser tab is not mistaken for a dropout.