I have played a similar game before, but this is also a nice implementation. After a while the challenge, which is not hard at all, becomes a little bit repetitive. Maybe you get smaller if you don't eat for a while? Like you are loosing weight? Maybe you can press shift to boost forward? Maybe you can temporarily gain size but if you don' eat during this period a number of mass, you loose weight, like a gamble? Maybe there are inkfish that leave a cloud, maybe there are fish which grow spikes at intervals and if you eat them during it you lose life etc. I just think the gameplay needs more variety. But the basics are in place and are nicely implemented.
I hope to see more and better of this.