Why losing waits a second
Pebble Merge does not end your round the instant a stone crosses the danger line. It waits. Two separate timers stand between a bad moment and the loss, and they are there because the first version, the one that ended you on contact, felt like the board had decided to hate you.
The first version ended you instantly
Early on, a pebble above the line was game over on the next frame. Simple to write, impossible to enjoy. You would drop a stone, it would settle a hair too high, and the round would end before your finger left the screen. The board felt like it was waiting for you to fail. Players do not say that out loud, but they stop coming back, and the reason they stop is almost never the difficulty. It is the meanness. An instant loss reads as mean even when it is fair, because the player never got a breath to see it coming.
I noticed it in myself first. I was testing a build and lost to a spawn I had not even looked at, and my reaction was irritation at the game, not at my own play. That reaction is the whole signal. If I, the person who wrote the rules, feel cheated by them, a stranger has no chance at all, and I have learned to treat my own irritation as the most honest review the game will ever get, more honest than any playtest note because it arrives before I have time to defend anything. So I went looking for where the meanness lived, and it lived in the absence of any pause between the board being in trouble and the board declaring you dead, a pause I had simply never thought to add because the lose condition felt obvious and obvious felt finished.
Two numbers stand between you and the loss
The first is a grace period for freshly spawned stones. A pebble that just appeared cannot count against you for 1000 milliseconds. The code calls it OVERFLOW_GRACE, and the check is blunt: if the stone is younger than that, it is not a threat yet, full stop. The reason is that a bad spawn is not your fault. You did not place that stone high. The generator did, and a generator should not be allowed to kill you before you have read the board it handed you. One second is the window where you can place the next drop to relieve the pressure instead of being punished for a spawn you never chose.
The second timer is the hold. Even after a stone has cleared its grace and is sitting settled above the line, the round does not end the moment it arrives there. The overflow clock has to accumulate 900 milliseconds of continuous breach before the game is over. That constant is OVERFLOW_HOLD. So the fastest possible loss from a single unlucky spawn is roughly 1000 plus 900, about 1.9 seconds, and in practice it is longer, because you are dropping stones the whole time and each good drop resets the feel even if it does not fully clear the line.
Both numbers are smaller than they sound. Two seconds is not a lot of time to a person who is panicking, and I do not want to oversell a single breath. But two seconds is everything compared to zero, because zero is the board deciding for you and two is the board asking you to decide, and the distance between those two feelings is the entire game, the difference between a player who hits retry and a player who hits close, and I have watched both happen to the same person on the same afternoon depending only on whether the loss arrived with or without a moment to react.
Four conditions before a stone even counts
The breach test has more gates than the two timers suggest. A stone only counts as a threat if it has landed and is not already consumed, if it is past its grace period, if it has stopped moving, and if its body is actually above the danger line. A pebble still falling does not end you. A pebble still sliding does not end you. A pebble that just appeared does not end you. Only a stone that is settled, old enough, and genuinely over the line, and has been that way without relief for nearly a second, ends the round. I like that sentence. It is the game being patient on purpose, and patience is a design choice, not a side effect, the kind of choice that shows up in the code as a number someone had to defend in a review rather than as a feature someone had to invent, which is how I have come to tell the two apart. A game that waits is a game someone chose to wait, and a game that ends you on contact is a game nobody bothered to ask the question.
The settle check is the one players never see and always feel. If we ended the round the moment a stone's center crossed the line while it was still rocking from the impact, fast cascades would kill you mid chain, which is the exact opposite of the feeling we want, because a chain is the best moment in the game and ending it mid chain is the worst possible punctuation. Requiring the stone to be still means the line is a real boundary, not a coin flip on the physics step.
The zen mode reuses the same clock
There is a no fail variant where the board sheds its highest stone instead of ending the round. It uses the same 900 millisecond hold to decide when a stone has overstayed its welcome and should be quietly removed. I did not have to pick that number twice. The calm mode and the losing mode agree on what counts as too long above the line, because "too long" is a property of the board, not of the stakes, and a board that sheds at a different threshold than it loses at would feel like two different physics engines wearing the same skin. One clock, two consequences.
I almost gave zen a longer hold, on the theory that a relaxed mode should be more forgiving. Then I realized the hold is not about forgiveness. It is about honesty. The line means the same thing in both modes, and the only difference is what happens after the hold expires. Keeping the number shared kept the world consistent, and consistency is what makes the relaxed mode feel relaxed instead of arbitrary.
Losing should feel like your fault
The principle underneath both timers is narrow but I use it everywhere now. A loss should be something the player did, not something the board did to them while they were still reading the situation. The grace protects you from spawns you did not choose. The hold protects you from the single frame where a stone tips over before you have reacted. Together they convert "the game ended me" into "I let the pile climb past where I could save it," and those two sentences produce completely different people at the retry button.
One of them comes back. The other one closes the tab. We picked the timers so the first one is the one who shows up next time, and the cost was two constants and a willingness to look at our own irritation and treat it as data instead of mood. The board is allowed to be hard. It is not allowed to be sneaky. The 1000 and the 900 are how we keep that promise in code.