The river shows you which houses it will take. You have five shovel-hours to change its mind.

The first spade changes nothing

Play the demo first. The next few paragraphs are the answer.

Water comes off the mountain at the top of the map and runs downhill toward the village. Left alone, it fills the low ground by the houses. Nothing happens for three turns. On turn 4, two houses go under, and the third goes on turn 5.

West of the meadow there's an old quarry, deep enough to hold the whole rise. A lip of ground keeps the water out of it, and it takes two spades to cut through.

Dig that lip once and all three roofs stay red. That's the moment I like best in the game: an hour gone, and three red roofs still there.

Dig it a second time and all three roofs go out at once. Let the river go and it pours into the quarry, twelve droplets over six turns, landing exactly where the blue rings said it would.

That's two shovel-hours, the warden's par. There's a cheaper save on this map, and the warden doesn't know it.

Seeing it isn't saving it

If the game shows you everything, the hard part is the budget. I wrote bots that play by the same rules you do, to test that. One of them, the ditcher, plays without a plan: each turn it checks the forecast and spends shovel-hours one at a time on whatever helps most right now.

On the second rise, no single shovel-hour saves anyone. I checked all 268 legal ones. So the ditcher spends its one dig keeping a field dry, and the river takes all three houses.

The ditcher does get one perfect rise. On the fourth, it heaps a berm on turn 1 and digs on turn 4 with the water already moving, and beats the warden by an hour. Waiting isn't always wrong. Over the season, though, it loses 8 houses the engineer keeps, looking at the same forecast.

Bots, not people. It has no players yet. The bots are in the game's source at /play/src/sim/hands.js.

Two rules, and you know the first one already

You don't need a manual. There are two rules that matter.

First: water runs downhill and fills whatever low ground it finds, then spills over the lowest edge. You'll see that in about four seconds.

Second: wet ground refuses the shovel. Try to dig a tile with water on it and the game says The water's already there. So the cheap fix is almost always early, while the ground is still dry. By the time a house is in real trouble, the ground you needed is usually under water.

The rest is forgiving. Undo is free until you commit. Press H and the warden's ghost shows you his plan, faintly, with no penalty. There's no game over: the flood always ends and you always see your grade.

OLD MERTEN, the retiring warden, coaches you through the first rise and only moves on when you do the thing he asked. Nothing moves until you let it.

Six rises, two valleys

A rise is one flood. The river comes up for six to nine turns, then it's over and you get your grade.

The first three rises are on THE BOTTOMS, the map in the demo. From there the water doubles on the second and triples on the third: 12, then 24, then 36 droplets. On the second, the quarry alone won't drink it all, and its opening note says what to do: When the ground won't go lower, it can go higher. That's the berm. Heap a tile one spade and it holds back one spade of water.

Fields complicate things. You can dig a field or flood it on purpose; you can't touch a house. On the first rise, one berm east of the meadow saves every house and drowns a field. So a field is something you're graded on, and also a basin you can spend.

The last three rises move to MILLER'S FORK, where the river splits in two and there are roofs down both arms. Rise 5 gets four shovel-hours instead of five. Its note: Count what it holds before you promise it the whole rise. And the last one is the crest. This is the flood they'll name the year after.

Three stars, and a par you can beat

• THE VILLAGE every house dry.
• THE HARVEST every field dry.
• THE SHOVEL the clean save, within one hour of the warden's par. It only counts with the other two.

Earn all three and the report reads A DRY VILLAGE AND A FULL BARN, then The warden nods. That's all he does, but he nods.

The warden's par comes from a computer search in the game's tests, not a guess. That search only looks at plans dug before the first drop, near the water's path, and it has a blind spot. I reran it over every tile. On rise 1 there's a one-hour save it never found, and on rise 2 a two-hour one. Rises 3 to 6 held against every early plan. Rise 4 falls only to a dig made mid-flood, which the search never tries. That's how the ditcher beat it.

Beating par still earns THE SHOVEL. The report prints the hours either way.

For anyone who has actually dug a ditch

It's a puzzle, and the water is simple on purpose. Here's how simple.

• The map is a 15 by 10 grid of whole heights, 0 to 9.
• Water arrives as droplets. Each one runs downhill a tile at a time and settles where it can't go lower. It takes the first lower tile it finds, checking north, west, east, then south, and doesn't look for the biggest drop.
• Nothing soaks in or evaporates. The map's edges are walls.
• The county regrades your work between rises, so each rise starts fresh.

What I think it gets right: a basin fills to its lowest edge and then spills, and an hour of digging in the right place beats ten in the wrong one. The red roofs and blue rings aren't estimates. They come from running the same engine ahead, and the tests check that the promise and the result match on every turn of every rise.

Honest gripes

• It's six floods, and then the season's over. No random maps, no daily.
• Rises 2 to 6 need a real keyboard and mouse. The demo works on a phone; the game doesn't yet.
• Your shovel work resets between rises. I'd like it to carry over. It doesn't.
• The par on rises 1, 2 and 4 is beatable, as above.
• It has no players yet, so I can't tell you how long it takes.