Grow a reef back. Keep it through the heat.

STAGHORN is a free reef restoration incremental that plays in your browser. You start with a dead reef: rubble, algae over bare rock, and four old brain corals that lived through whatever killed the rest. Rope trees in your nursery grow coral fragments, and you plant them on the seabed one cell at a time. Every summer the water gets a little warmer.

Three things that pull against each other

  • The reef. A 14 by 8 seabed of sand, rock and rubble. Fragments hold on clean rock; loose rubble needs a steel frame first; nothing settles on sand. A grown colony spreads into the clean rock beside it.
  • The fish. Living coral brings fish. Fish graze the algae that smothers bare rock, and snorkellers pay to see them. That is your funds. The more kinds of coral on the reef, the more they pay.
  • The water. When the water climbs past what a coral can bear, it bleaches: it turns white and stops growing. If the heat goes on, it dies, and its skeleton is left for the algae.

The survivors come back hardier

A coral that bleaches and lives hardens, and your nursery keeps cuttings of the hardiest line. Every third summer from year 5 is a marine heatwave. The first one will hurt. What you plant after it decides whether the reef holds the next one.

Four corals, four jobs

Staghorn grows fast and bleaches first; autumn storms break it, and the broken branches can take hold where they land. Table coral grows a wide plate that shades the cells beside it. Brain coral is slow and tough and shelters its neighbours from storms. Pillar coral stands between them. Unlock the lines, more trees, urchins, a temperature buoy, a dive team, a visitor centre, a heat hardening lab and spawn nets as the reef comes back.

Nothing restarts

It saves as you go. While you are away the reef keeps living, up to one season, heat and all. A colony that dies leaves its skeleton to clean and replant, never a restart.

Controls: tap or click. 1 to 4 pick a coral line and plant, S scrubs algae, R lays a frame, the arrow keys and Enter plant from the keyboard, T changes tabs, F toggles 3x speed, P pauses, H opens the help, M turns the sound off. Plays on desktop and phones; on an upright phone it switches to its own tall layout. About twenty minutes to the goal at normal speed.

Paid, from the same studio

  • LINGUIST OF THE DEEP ($9.99): swim an alien reef, overhear its creatures speak in light, and learn their language.
  • ROOTWORK ($5.99): grow a seed's roots down to every pool of water, where every cell of root costs sugar.
  • GLASSWRIGHT ($9.99): run a medieval glassworks, where every window you complete is drawn by the game.

Credits and disclosure. Made by Core Systems Asset Factory. Code and text were written with AI assistance. Every picture in the game is drawn by code written for it: every coral, fish and turtle, plus three seabed plates from our procedural pixel engine. The cover is composed from the game's own renderer. The music and the sound effects are synthesised by code, with no generative audio model.

More free browser games: GASHOLDER, COMBWRIGHT, CLERESTORY. Everything we make: csaf.itch.io.

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