About
Eat Small. Grow Huge.
Critical Mass is an online cell survival game built around one simple rule: bigger cells eat smaller cells.
You start each life near the bottom of the food chain. Collect pellets to gain mass, chase players small enough to consume, and stay away from anything that can consume you. Larger cells are powerful but slow, so getting bigger does not automatically make you safe.
There is no round timer. Your life continues until every one of your cells has been eaten.
The Arena
Move with your mouse or controller stick and your cells will follow. Small cells move quickly. Large cells take longer to turn and accelerate.
The basic controls are easy to learn, but using them at the right time is what keeps you alive.
- Consume pellets and players: Food provides steady growth, while consuming another player can completely change your position on the leaderboard.
- Split your cells: Launch half of your mass forward to catch prey or escape danger. You can control up to 16 cells at once, but every split creates another vulnerable piece of you.
- Eject mass: Give mass to another player, use it as bait, or fire it into a virus.
- Use viruses: Large cells that consume a virus burst into smaller pieces. Feeding a virus enough ejected mass causes it to divide and launch another virus across the arena.
- Merge again: Split cells can eventually combine back into a larger cell if you manage to keep them alive.
Public and Private Matches
Public matchmaking places you into an active lobby or creates a new one when necessary. Lobbies support up to 64 players.
Bots fill empty spaces so a standard public arena stays close to 28 active competitors. They collect food, avoid larger threats, hunt smaller cells, use split attacks, wear collectible skins, and return after being eliminated. As more human players join, bots make room for them.
You can also create a private match and share its six-character lobby code with friends.
Private hosts can:
- Enable or disable bots
- Choose 0.5x, 1x, 2x, or 3x pellet density
- Invite players with a lobby code
- View everyone currently connected before entering the arena
Persistent Progression
Your current size disappears when a run ends, but your profile progress remains.
Standard matches award experience and coins. Your profile tracks:
- Highest mass reached
- Longest survival time
- Total pellets consumed
- Total players consumed
- Matches played
- Wins
- Lifetime survival time
There are 36 achievements covering basic milestones, enormous runs, player eliminations, split challenges, pacifist runs, daily rewards, rivalries, and cosmetic collection.
Daily rewards increase over a seven-day streak. Achievement rewards and match earnings provide coins that can be spent in the skin shop.
If the same player repeatedly ends your runs, they can become your Nemesis. Their name is saved to your profile, highlighted in the kill feed, and tracked until you defeat them.
Global leaderboards are available for:
- Pellets consumed
- Biggest mass
- Players consumed
- Longest survival
- Matches played
- Mass ejected
Colors, Skins, and Custom Cells
Choose from 10 free cell colors at any time. Colors are separate from skins, so you never need to purchase a basic color change.
The cosmetic collection contains 39 choices, including the Eight Ball, Penguin Pop, Rubber Duck, Baby Dino, Black Hole, Radioactive Ladybug, Arcade Cabinet, Dragon, Ghost Skull, Plague Doctor, and many more.
Skins are cosmetic. They do not provide extra speed, mass, damage, or other gameplay advantages.
The World Flag skin includes a searchable collection of 255 countries and territories.
The Open Canvas skin lets you place a direct image URL inside your cell. Images are automatically cropped to fit the circular shape. Custom images are disabled by default, and every player can choose whether they want custom images to appear.
Controls and Settings
Critical Mass supports mouse and keyboard as well as controller play.
- Mouse or left stick to move
- Mouse wheel or controller bumpers to zoom
- Space or controller A to split
- W or controller X to eject mass
- Enter to open match chat
- Escape or the controller menu button to pause
Settings include adjustable UI scale, master volume, arena grid visibility, exact mass display, reduced skin motion, high-contrast interface edges, and custom image visibility.
Enter the arena, choose your fights, and see how big you can get.