Cool concept! I really like the mechs art and the surroundings, some more natural obstacles than white stretched cubes would be nice, maybe rocks for example or some batches of tress? Other than that I see you know whats still missing, like UI, also some healthbars for enemies and means to heal yourself up (or rather - fix yourself up) apart from killing enemies would be nice, its hard not to die on the second enemy depending on how many cannons you spawned with (or so I assume) :D From my personal opinion as well - I would free the camera more - when firing missiles its a little bit annoying that you cant see clearly forward, but semi - top down view with a bit of forward space ahead of you. Also if you want to add gravity to the bullets - add more power to them and try to draw a line while aiming for player to see where his missile will drop! Could be useful and fun mechanic that adds a little bit to mech theme of it - measuring power you need to fire and so on :) Also adding some offset to enemies aim would be nice, as far as I can see, they are too accurate right now, so they have advantage over the player!
I would love to see it finished one day! Good job so far! :)