Browser city-builder on real sea-level dataOct 2026

Saltmere

A browser city-builder about coastal prosperity and rising seas, driven by IPCC sea-level curves.

My partSet the game design, the climate model's rules and the acceptance tests, and played every release.

Agent-heavyAgents wrote most of the code.

Play Saltmere

A low-poly coastal port town by the sea, with the game's controls around the edges — Saltmere, a fictional port town, in 2025.

410 playersin its first 22 days, about 40 minutes a session (as of 13 Nov 2026)

What it does

Sea level follows IPCC AR6 projections for a real tide gauge (Hoek van Holland). You choose SSP1-2.6, SSP2-4.5 or SSP5-8.5 at the start, and it's fixed for the campaign.
Water is simulated, not scripted: floods follow connectivity and levees, pumps move water back to the sea, and the water balance is checked exactly in tests.
Four kinds of response, each with visible limits: protect (levees, pumps), accommodate (raise), retreat (build inland, buy out) and nature-based (salt marsh, dunes, living shorelines).
The town's newspaper reports what happened, with short notes on real events, each from a source that was opened and read.
Runs in the browser on desktop and phone, tested in Chrome, Edge, Firefox and WebKit; 16 releases since launch on 22 October 2026.

How I checked the agents' work

A data contract before any code

The science notes came first. For each dataset they record the source, version, retrieval date, location, baseline, units, licence and every transformation step, and they say what the game gets wrong.

Example: after 2100 the sea is held at its 2100 level, which understates it, and the in-game report says so.

Source: docs/science-and-assumptions.md

Screens

The same harbour district side by side in 2025 and in 2090, flooded at a spring tide — The same streets in 2025 and at a spring tide in 2090.

The town with low-lying land shaded orange by the flood-risk lens — The flood-risk lens.

The town newspaper reporting a storm tide, with a note on a comparable real event — The Saltmere Gazette, with a sourced real-world note.

An end-of-campaign report summarising a century of sea-level rise — The campaign report.

Shares a stack with

TypeScriptKloisterproject tracker

React · agent-writtenReeldexmedia library