So if you press space you split in half, that is used to either escape for to quickly eat those who are smaller than you. If you are huge and crash into the green balls, it will explode you into a bunch of balls which is really bad because then you are a big target. If you are small, you can hide inside the green balls. And over time after you split, you do merge back together, but not immediately.
~16
Also, if you press W, you fire a small portion of yourself that you cant control and others can take. I don't understand how it would ever be useful though.