About Mycelium

Mycelium is a free territory strategy game that runs in your browser, an .io game in the same family as OpenFront and Territorial.io. You play as a fungus spreading underground, competing with other colonies for soil, nutrients and survival.

The idea

Territory games are simple to explain: grow, take land, beat everyone else. Mycelium adds one rule taken from real fungi. Your colony is a network, and a network is only as strong as its connections. Every part of your territory has to stay linked to your origin. When an enemy cuts through a thin strip of your land, everything beyond the cut withers away.

That one rule changes how you play. Size alone doesn't win: a huge colony with a weak neck can lose half of itself in three seconds, and a small player who finds that neck can turn the whole match. Every match becomes a game of shapes, chokepoints and well-timed cuts.

Real fungi, real networks

The game is a cartoon of something real. A mushroom is only the fruit of a fungus; the fungus itself lives underground as mycelium, a web of microscopic threads called hyphae. Those threads spread through soil and dead wood, breaking them down and carrying water and nutrients across the whole network.

Mycelium networks can get enormous. One honey fungus (Armillaria ostoyae) in the Blue Mountains of Oregon, in the United States, is thought to cover nearly ten square kilometres, which makes it one of the largest living organisms ever found. (Yes, one of the bots is called Honey Fungus.)

Many fungi also link up with plant roots in partnerships called mycorrhizae: the fungus brings water and minerals to the plant, and the plant feeds the fungus sugars. These underground links between trees are sometimes nicknamed the "wood wide web". In the game, nutrient soil and rotting logs are a nod to how real fungi feed, and roots, islands and rival colonies are a playful take on how they compete.

All 64 bot names come from real fungi: Chanterelle, Lion's Mane, Turkey Tail, Death Cap and many more.

Who makes it

Mycelium is made by one independent developer. It started as a prototype on October 8, 2026, and has been updated almost every day since. You can follow every change on the updates page. Ideas, bug reports and feedback are very welcome at myceliumplay@gmail.com.

Frequently asked questions

Is Mycelium like OpenFront or Territorial.io?

Yes, it belongs to the same family of territory .io games: you send a share of your resources to grow, take land from your neighbours and try to be the last one standing, in real time, against bots or other people. The big difference is the supply-line rule: your territory is a fungal network, and anything cut off from your origin withers in three seconds. That makes shapes, chokepoints and well-placed cuts matter as much as size. Mycelium also has abilities (spore bursts and mycotoxin) and eight map styles, including islands and root highways.

Is Mycelium free?

Yes, completely. There is nothing to buy, no account to create and nothing to download.

How do I learn to play?

The game offers a two-minute tutorial on your first visit, and it's always available next to the Start button. For the full rules, read How to play, then the strategy guide.

Can I play with friends?

Yes. Choose Online, create a room and share its four-letter code. Up to eight colonies fit in a match: your friends plus as many bots as you like. The room stays open after each game, so you can play again right away. Quick play puts you in a public match with anyone online.

Can I play alone?

Yes. Solo matches are against one to seven bots, with four difficulty levels from Easy to Brutal, on any of the eight map styles and four sizes.

Does it work on phones?

The game loads on phones and tablets, but it is designed for a computer with a mouse: the right-click menu, precise clicks and the keyboard shortcuts make it much easier to play there.

Can people cheat online?

Every player's browser runs the same simulation, and the game server runs its own copy and checks every move. A modified page can't make you send biomass you don't have or act for another player.

Why does my online click take a moment to happen?

Online, every click goes to the game server and back before it takes effect, so that all players see exactly the same match. The game shows your target right away, and the growth starts a fraction of a second later, depending on how far you are from the server.

What data do you collect?

Very little: no accounts, and visitor statistics without cookies. The details are in the privacy policy.