I finished the game in 10 minutes.
It felt pretty slow at the beginning, and the timer wasn't clear. So, in the first few levels, I'd manage to capture a few pieces of biomass within the allotted time, but the timer would run out and the game would end. As a player, in the early stages, I felt like I was losing and doing something wrong.
I liked the creep mechanics in the middle game; it was really cool to watch them run.
In the late game, I really liked the feel of the effects (explosions, numbers, splashes).
Overall, the effects are cool, but the timer mechanic wasn't so great.
I suggest replacing the timer with health—for example, a virus would fly through space and lose health upon collision with biomass, or enemies would immediately appear. The goal is to create some kind of challenge and make the player feel like their actions influence the outcome.
Good luck with the game!