Every tile is a real American-mahjong tile, and the grid of tiles is the sea wall, laid clear across the coast. Swells run in from the water and break against the footing; every one that lands tears a brick out of the wall and pushes the tide up. You have one cannon, one minute, and a wall full of ammunition.
Tap a tile and that brick comes out of the wall and into the chamber. Three bricks is a full load. The hole it leaves behind is a gap: water is already coming through it, and every open gap makes the tide climb faster. That is the whole trade — the wall you are stripping is the wall holding the water back. Tap a gap to relay the brick by hand if you need it closed right now.
The chamber reads as a mahjong hand and the cannon fires it. One brick is Grapeshot. Three of one suit is a Broadside. Three of a suit in a row, like 4-5-6 Dots, is a Shockwave that shoves every swell on the water back. Three of a kind, like 5-5-5 Bamboos, is Armor piercing — twenty-six damage, and it carries through to the swell behind the one you hit. The readout under the chamber tells you what is loaded and what it hits for.
A dying swell throws water into its neighbors, and anything that dies from that keeps the chain going. Six hits in a row loads the tidal cannon: fire it anywhere and it clears the water, drops the tide eighteen points and relays every gap in the wall. Chains are where the score comes from — every link in the chain pays more than the last.
The swells get faster and tougher as the tiers climb, and every ninth one is a storm surge: big, red, and it takes three bricks when it lands. The orange haze over the city thickens as the carbon budget drains; let it hit zero and the black tide comes in. Windows go dark floor by floor as the water rises, and the cars and people on the avenue behind the wall stop moving once the water goes over the top.
The run ends when the tide goes over the wall. Shoot the swells early, keep the chain alive, and remember that a gap you opened yourself is still a gap.
Tilewatch is an independent practice game. It is not affiliated with the National Mah Jongg League (NMJL); the current official NMJL card remains the final authority on every rule. Storm surge and sea-level rise are real risks for low-lying coastal cities — the numbers here are simplified to make a playable minute.