Capture every opponent's head square. The last player with a living head wins.
Each turn you place the current tetromino shown in your hand. The piece must be placed orthogonally adjacent to territory you already own and cannot overlap any occupied cell. Use R to rotate before placing.
After you place, any run of enemy cells flanked on both ends by your cells — in a row, column, or diagonal — is captured and becomes yours. Board edges don't count as walls.
Every cell must stay connected to its owner's head square through a chain of that player's cells. Any cells cut off from the head are removed from the board immediately after each move.
Press B (or the Bite button) then click an enemy cell orthogonally adjacent to your territory to eat it. Each player has a limited number of bites. Biting counts as your whole turn.
The four corner squares each hold a bonus bite, shown as a glowing diamond. Grow your fungus onto a corner to collect it and add one bite to your supply.
You may only pass if you have no legal placements for your current piece and no bites remaining. If both conditions apply you are auto-skipped.
Click Resign at any time to forfeit. All your cells are immediately cleared from the board and you are eliminated. Click twice to confirm.
| R | Rotate piece |
| B | Toggle bite mode |
| Esc | Cancel bite mode |
InternetFungus is based on NetFungus by Andrew Schaaf, itself inspired by Fungus by Ryan Koopmans.