It rises when you act, not on a timer. Every move you make — rowing, sandbagging, roping, breaking something open, firing the flare — advances the flood one step, and the level tells you how many moves each step takes. That means you can sit and think for as long as you like without losing anybody, and it also means there is no such thing as a free move. In the last chapter storm surges add a second, irregular rise on top of the first, so the rhythm changes even though the average speed does not.

Because nearest-first is the trap the whole game is built around. The countdown on each roof comes from how far that house sits from open water at the start, and the farthest villager is given the shortest fuse, so the people who look safe because they are close are usually the ones with the most turns to spare. Read the numbers before you read the distances. A pilot that always goes to the closest person fails fifty-eight of the sixty levels.

It buys turns for a house you cannot reach yet. Dropping a bag on a roof raises it, which pushes back the turn the water closes over it — but placing it is itself a move, so the flood climbs while you do it. It is worth it when one long trip would otherwise cost you somebody on the way back, and it is a waste when the deadline was never going to be the problem. Working out which of those you are looking at is most of the middle of the campaign.

Two — and that limit is the reason the game is a route puzzle rather than a collection run. A heavy passenger fills both seats on their own, so sometimes the boat is full with one person aboard. When it is full nobody else can climb in, and the counter at the top of the screen turns red and says so; the only way to make room is to row to the barge and drop off who you have. Planning that return trip into the route, before the water closes the channel you came in by, is most of the difficulty in the later chapters.

Yes, and it is checked rather than assumed. Each level is generated and then repaired until a reference pilot can clear it, and that same pilot is what the hint button runs, so a hint always shows a move that is on a route to finishing. If you are stuck, two hints per level are free before the game offers to trade one for a rewarded ad, and undo is free three times.

No download, no account, no purchase. It runs in the browser on desktop and on mobile, and because it is turn-based it plays perfectly well with one thumb — every action in the game is a single tap on a tile, and the tile you tap decides which action it is. Keyboard players can use the arrow keys and Enter, with U for undo, H for hint and P to pause. Progress is stored locally on the device you play on.