Ing, NHK and Progressive time controls
Three Go time systems sit outside the common ones. Ing overtime lets a player buy up to three extra periods, each costing 2 penalty points on the board. The NHK format gives 30 seconds per move backed by ten one-minute reserve periods, and is the basis of Japan's best-known televised Go. Progressive overtime is Canadian overtime whose stone quota grows with every completed block. All three are implemented in Byoyomi Timer.
Ing overtime: paying for time with points
The Ing rules, backed by the Ing Chang-Ki Weiqi Educational Foundation and recognised in the European Go Federation's tournament rules, handle time trouble in a way no other system does: instead of ending the game, you buy more time and pay for it in points.
- When your main time expires, you may take an overtime period. Each period lasts one sixth of the original main time — 10 minutes for a 60-minute game.
- Each period taken costs 2 points, deducted from your score at the end of the game.
- You may take up to three periods. Overrunning the third loses the game on time.
A player can therefore trade up to 6 points for up to half an hour of extra thinking in a 60-minute game. In a close game 6 points is decisive; in a game you are winning by 20 it is a bargain. That turns time trouble into a genuine strategic decision rather than a pure threat, which is what makes the system interesting.
A clock can count the periods and total the penalty, but it cannot apply the points — scoring happens on the board during counting. Byoyomi Timer therefore displays the accumulated penalty and leaves the arithmetic to the players, which is the only honest thing a clock can do here.
The NHK format: 30 seconds and ten lifelines
Japan's public broadcaster NHK runs a long-standing televised Go tournament, and its time control is built for television: games must fit a broadcast slot, but must not be decided by pure speed.
The format is 30 seconds per move, with ten one-minute reserve periods a player may call on when 30 seconds is not enough. There is no main time at all — the clock is a per-move deadline from move one. Using a reserve consumes it permanently; the ten reserves are effectively ten lifelines for the whole game.
Watching it is unlike watching any other Go. Professionals play most moves within the 30 seconds, so the game moves at a steady, almost musical pace, punctuated by the moments a player visibly decides to spend a lifeline. Mechanically it is time-per-move with reserve periods, which is why Byoyomi Timer implements it as a preset of its per-move system rather than a separate mode.
Progressive overtime: the quota that grows
Progressive overtime is Canadian overtime with an increment on the stone count. Every time you complete a block, the next one demands more stones in the same amount of time:
| Block | Stones required | Time | Average per stone |
|---|---|---|---|
| First | 15 | 5 min | 20 s |
| Second | 20 | 5 min | 15 s |
| Third | 25 | 5 min | 12 s |
The pressure ratchets up the longer the game runs, which suits Go's structure: late-game moves are more forced and can genuinely be played faster. It is used at events in East Asia and is close to unknown in Europe and North America — but since it is one parameter away from Canadian overtime, there is no good reason for a clock not to offer it.
Why implement systems this rare?
Because the players who need them have nowhere else to go. A club running an Ing-rules event, or a group wanting to play the NHK format they watch on television, will not find these on a chess clock or in most timer apps — and the logic, once byo-yomi and Canadian exist, is modest.
The reverse is also true: Byoyomi Timer deliberately does not implement Bronstein delay or hourglass mode. Both are chess systems with no meaningful use in Go, and including them would clutter the picker for every Go player to serve nobody.
Turn your iPhone into a real Go clock
Byoyomi Timer plays every Go time system — byo-yomi, Canadian overtime, Fischer bonus time, Ing — and reads the seconds aloud like a human timekeeper.
Coming soon to the App Store