Hello!
Well, Spinatus definitely has the bones to be a good game.
Well implemented mechanics, timed implementation. Really enjoyed playing it.
Ignoring art and art, as you asked us to, my suggestions for you, as it is in very early development is:
1. Connectivity between actions. Shoot, special and Q ability for instance should allow the player some interaction and connectivity between them, like shooting while charging or holding the special at max, IMO those abilities should interact with each other to make the gameplay really flow;
2. Some meta progression to "control" a bit more the robots cannon direction, power, etc;
3. I think this game can really shine with juiced up actions, everything should have an impact, I'd work towards that as well.
All and all, I think Spinatus might be a good game since it has the bones to it. Good work on it!