I like those very Mech Warrior inspired designs :D
and the dynamic music to alternate between attack waves and prepping at the base is also a nice detail.
Gameplay has some solid stuff, as well as some issues :
I like the fact that it's mouse aiming to have great precision, however i feel the angle you put your camera at doesn't really help, i think this could be improved if you put it a bit higher up and pointing a bit more down to get a better idea of the 360 area around your mech.
Also the enemies do seem to have quite an unfair advantage in that they fire imediately from offscreen and can take potshots at you and the base before you can really see them.
But on the solid side with the mouse aiming i'll add the neat arrow indicating your mech's front since you made the walking tank like and thanks to this it works well and avoinds confusion to as where you're facing ^^
Overall despite the small issues it's a cool game and i think with a few fixes it has some solid bases already in place, so good job to you :)