Sand Fall

Eight grains wait in a hopper above three gates and four chambers. Each chamber carries a mark — the amount it is asking for — and the gates decide where the next grain lands: the top gate picks a half of the row, the gate beneath it picks one of that half's two chambers. Swing the gates, let a grain fall, and repeat until all four chambers are exactly on their marks. There is no timer, no move limit and no way to lose. Sand that sits at or below a chamber's mark has settled and stays put, so nothing you have already got right can be knocked back out — the only thing a mistake costs is a grain scooped off and poured somewhere better.

It runs entirely on your device: 0 network requests, works offline. No ads, no account, nothing to buy, and no betting, money or prizes of any kind.

1. Focus the board — click it, or press Tab until it is outlined.
2. Aim with ← and →. The flow moves one chamber at a time and you can watch which gates swing to make it happen. Shift flips the top gate on its own, which crosses to the other half of the row in a single press.
3. Let a grain fall with ↓, or Enter. It lands in the chamber the gates are pointing at and the hopper drops by one.
4. Scoop one back with ↑ when a chamber has gone past its mark. Only sand above the mark can be taken back; everything at or below it has settled.
5. Read the glyphs. ▽ means the chamber is still short, ▲ means it has too much, ✓ means it is settled. The number under each chamber says exactly how much it holds and how much it wants, so nothing here depends on telling tints apart.
6. Finish when all four chambers show ✓. Compare your moves against "fewest possible" if you want a target, or ignore it and take as long as you like.

Using a mouse or a touchscreen instead: press a chamber to aim at it, the spout to drop a grain, the scoop under a chamber to take one back, and any gate to swing that one gate on its own.

How do two gates decide which of four chambers something falls into?

By spelling the chamber's number in binary, one bit per gate. The top gate is the first bit: left sends the grain to chambers 1 and 2, right sends it to chambers 3 and 4. Whichever gate it feeds is the second bit and picks one of that pair. Two gates therefore name four destinations — and the top gate is worth two of the lower ones, so crossing the middle of the row is one press while shuffling along inside a half is another. That is also why the third gate is doing nothing at any given moment: only one of the two lower gates is on the path, and swinging the other changes nothing until the top gate swings first. It is the same idea as an address in a computer, a postcode, or a knockout draw — each branch halves what is left.

Can I get stuck, or lose?

No, and not by luck — by construction. Sand is conserved: a grain is only ever moved between the hopper and a chamber, so the total never changes and it is always exactly the sum of the four marks. Any chamber that has gone over its mark can always be scooped back down to it, and once that is done the hopper holds precisely what the short chambers are missing. So the finished board is reachable from every position you can possibly reach, including the silly ones, and there is no fail state to warn you about.

How do I know the board can actually be finished?

Because it was built backwards from the finished board. The generator fills every chamber to its mark first — the solved container — and then lifts grains back into the hopper one at a time. Pouring those grains back where they came from is a solution, so one exists before you ever see the board. The single chamber that starts with too much is put there on purpose, so that scooping is part of every board rather than a control nobody discovers.

What does "fewest possible" mean, exactly?

It is the true minimum, worked out rather than guessed. Every move shifts one grain between the hopper and one chamber, so it changes one chamber's distance from its mark by exactly one — meaning no route can be shorter than the sum of those distances. That sum is always achievable too, so the number shown is exactly it. A grain sitting in the wrong chamber therefore costs two moves, one to scoop it off and one to pour it back: that is the whole reason to aim before you drop.

Is there any money, betting or in-app purchase in this?

None, and there never will be. No currency, nothing to buy, no lives to refill, no prizes, no wager of any kind. The game is the whole product.

Does it work offline, and can I play it with a keyboard or a screen reader?

Yes to all three. Once the page has loaded once, the whole game is on your device — the gates, the marks and the arithmetic that works out the minimum — and nothing is sent anywhere at any point. Arrows aim, ↓ pours, ↑ scoops, Shift crosses the row. A screen reader hears which gates are on the path and which way each is tipped, plus what every chamber holds against what it wants, so the board can be played by ear alone.

Four chambers, three gates, eight grains, and marks between one and three. The hopper is the only source and the chambers are the only destinations — nothing drains away and nothing new arrives. Sand at or below a chamber's mark cannot be taken back, so a chamber can only ever be overfilled by your own pours, never emptied by accident. There is a single board per seed and no difficulty ladder: every board asks for the same kind of thinking, and the only score is how close you came to the fewest possible moves.

Mirror Fold and Stone Drop are the other calm games here — also untimed, also impossible to lose, turning on symmetry and on sequencing rather than on routing. Water Jugs is the other puzzle about landing on an exact amount, and Pipe Flow is the other one about deciding where something ends up by setting the path rather than by moving the thing itself.

Bookmark this page (Ctrl+D, or ⌘D on Mac) or install the app — it works offline the next time you need it.