It's gotten to the case where all of the game's complexity is thrown at you right at the beginning. Maybe a form of progression in difficulty could help?

too easy for me...
some ideas:
-what about some store , you can buy upgrades with score points or even some new currency
-hard mode would be great
-sprint?
-some kick ass music !

Too basic for it's own good. Could really use more enemy types, maybe based on splitting cells? Also, the tutorial takes far too long for how simple the gameplay is.

Functional, but could be improved by making the enemies do more damage and not spawn in so close. Perhaps you mask it by having a radius of reduced visibility to simulate the cells detection range. Darken it up, as though it takes place in a body instead of a Petri dish, and maybe add some muffled internal noises or at least generic music/sounds so it’s less stark. Maybe throw in an upgrade system that takes you from B to C to Natural Killer.

Got to 10k. You needed more enemy variety for sure. 2 enemy types, it's too simple.
And the player is incredibly simple too (No attack or combat variation). I can't rate higher than this until you do more.