What Leviathan is
Leviathan: Evolve the Deep is a free merge game set in one living reef. You drop fish into the water from the top of the tank. When two fish of the same species touch, they merge into the next species up. Eleven species make up the chain, from a tiny Fry to the Cosmic Whale, and every one of them actually swims: it picks a heading, looks for a partner of its own kind, flees bigger fish and, once it is large enough, hunts smaller ones.
That last part is what makes Leviathan different from shape-dropping merge games. You do not stack pieces in a box. You stock a tank and then manage an ecosystem: the fish do the merging themselves when they can see each other, the predators thin out your small fry, and a red Spikefish swims in from the edge every so often to kill whatever it reaches first.
The goal
The goal bar at the bottom of the screen says it plainly: raise two Leviathans. The game marks two moments:
- Your first Leviathan brings up the "Leviathan Rises" card and counts as a win. You can keep playing straight away.
- Two Leviathans merged become the Cosmic Whale, the top of the chain. That is the full win: a bonus of 500 pearls, a victory card showing your whale in its actual colours, and the choice to start a new reef or keep admiring the one you finished.
Alongside that run goal there is a longer collection: the Abyssal Codex, with 66 entries (every species in its natural form and in each of five rare bloodlines), and 22 achievements. Both survive every new reef.
Quick start: your first five minutes
- Read the tank. A new reef starts with four small fish already swimming. The top band of the tank, about a fifth of its height, is the release zone. The HUD shows your pearls, how many species you have found this reef (out of 11) and a preview of the next fish you will drop.
- Drop near a twin. Tap inside the release zone and the previewed fish dives in at that spot. You can drop roughly three fish a second. The next fish is always a small one: Fry, Neon Tetra, Clownfish or Angelfish, with Fry the most common.
- Let them find each other. A fish that sees another of its own species swims to it and they merge. You do not need perfect aim, only to keep pairs close enough to notice each other.
- Watch the tank counter. The tank holds 14 fish to start. Free Fry also drift in on their own every few seconds while there is room, so the tank fills even when you are not dropping. When it is full, you cannot drop until merges make space.
- Spend your first pearls on space. Pearls come from merges and trickle in from every living fish. The first Bigger Reef upgrade costs 400 pearls and is the most useful early purchase.
- Get ready for the Spikefish. Once your reef has more than ten fish and you have played for about a minute, the first Spikefish arrives. The game pauses to explain it the first time. Tap it to net it.
Controls
| Action | Desktop | Touch |
|---|---|---|
| Aim the next fish | Move the mouse along the top; a faint guide line follows | Tap where you want it |
| Drop a fish | Click inside the release zone | Tap inside the release zone |
| Net a Spikefish | Click on it in the tank | Tap on it in the tank |
| Open or close the Reef Shop | Shop button, or Tab or S | Shop button |
| Codex and achievements | Menu button beside the shop | Menu button beside the shop |
| Settings | Gear button | Gear button |
Settings has separate music and effects volume sliders, a sound switch and a Reduced effects option. Opening the shop, the settings or a victory card pauses the reef, so you can browse without losing fish.
Questions
Is it free?
Yes. It runs in your browser with no download and no account. The two optional boosts, Pearl Rush and Mutation Surge, can be paid for with pearls, and nothing in the game needs them to reach the Cosmic Whale.
How does saving work?
The reef saves itself to your browser every few seconds and when you close the page, so it lives on the device and browser you play on. Clearing your browser data clears the reef.
Does the reef earn while I am away?
Yes. If you are gone for more than two minutes, your fish earn pearls at half their normal rate for up to eight hours, and a Welcome Back screen shows what they made. Bigger fish and fish with a bloodline earn more.
Can I play on a phone?
Yes. The tank refits itself to your screen and rotates with the device. Everything is done by tapping.
How long is a reef?
There is no timer and no game over. A reef lasts until you summon the Cosmic Whale or start a new one from the title screen. A new reef resets your fish, pearls and tank upgrades, but keeps your Codex, achievements and lifetime stats.
Where should I read next?
Start with the species chain to learn who eats whom, then merging and scoring for how pearls really add up.