Biome 3d is essentially a 3d version of agar.io, you play as a blob and wonder around the map eating the smaller blobs to increase your size, just remember that smaller players are edible too meaning if you coming across anyone bigger run as they're probably hungry!
If you're unfamiliar with this type of game its very easy to understand and a ton of fun to play, as I mentioned already you roam the world as a blob and look to consume others in order to grow bigger and stronger. Bigger blobs eat smaller blobs meaning you can eat any player smaller than you or be eaten by anyone bigger. You have the ability to drop mass in front of you which can be helpful to bait in smaller blobs or help them out if you're feeling generous, you can also divide your mass into 2 equal sized blobs and launching one forward to close a gap. This ability can be useful for either escaping or catching up to a faster opponent.
Movement is controlled with the mouse, the camera can be moved using WASD and space bar is used to split your blob into two.