A small water-management sim about one summer on a terraced rice hillside in Japan. Made for Game Gauntlet SIM Jam 2026 (itch.io, Sep 23 – Nov 4, 2026).
Twelve paddies step down a hill under one pond. You set the board in each field's outlet (that's how deep the field holds water) and open or shut three gates on the channel from the pond. Water above a board spills into the field(s) below. Whatever leaves the bottom field goes to the river, and the village downstream needs some of it.
The rice wants different depths as it grows: deep while it roots, shallow while it tillers, bone dry for the mid-season drying, deep again at heading, wet-and-dry while it ripens, drained at the end. Pond water is cold, levees wear out, moles dig, and the weather doesn't care about any of it.
Play: open index.html in a browser (no build step, no server needed). Desktop browser with a mouse is best.
| Click a field | select it |
| Mouse wheel / ↑ ↓ / right-click | raise or lower that field's board |
Click a gate on the channel, or I |
open / shut it |
| Click the sluice, or the panel button | release pond water to the river |
R |
repair the selected field's levee (3 of your 8 hours a day) |
Space / 1 2 3 |
pause / speed |
Tab |
next field |
M |
sound on/off |
English and Japanese are both in the game (button at the top right).
- Hourly water balance for a pond and 12 fields: stream inflow (more after rain), runoff from the hillside into the pond, rain on the fields, evapotranspiration (weather and temperature dependent), seepage through the levees (worse as they wear), board overflow cascading down a branching network, a legally required bypass share for the river.
- Water temperature in each field: stream water is cold, shallow water warms fast, so fields right under a gate run cold early in the season.
- Seven growth stages, each with its own depth band and sensitivity; cold-water stress; heat stress at heading that deeper water partly shields; mid-season drying counted in hours, with lodging if a field never dried.
- Levee wear, mole damage, bursts under deep water, typhoon damage, and a daily labour budget for repairs.
- The downstream village's goodwill, which falls when the river runs short. At zero they come up and open your sluice for two days.
- Three seeded years: ordinary, dry rainy season, typhoon year.
node tests/sim.test.js # 13 checks, incl. exact water conservation over a season
node tests/policies.js # a do-nothing player vs a careful scripted player, each year
index.html, style.css, js/sim.js (the model, no DOM), js/render.js (canvas drawing), js/audio.js (WebAudio synthesis), js/main.js (loop, input, panel), js/i18n.js (EN/JA text).
See docs/itch-page.md. In short: code and in-game text were written with an AI assistant and then reviewed and tuned by hand; all visuals are drawn by that code at runtime and all sound is synthesised by it. No image, music or voice generators were used, and there are no third-party assets.
© 2026 the author. All rights reserved. You're welcome to play it and read the source.