This is quite a simple game, but I like the efforts to add juice to the game ! The idea of having different shield for left and right is really interesting, it allows the player to prioritise one side over the other if the shield is lower. Maybe adding some shield regeneration if it is not hit for a while could make it even more strategic ?
You could add even more juice by changing the color of the enemy hit for some time, maybe slowing it down for a bit ? The screenshake is cool, but you're doing it in a way that doesn't feel natural. It took me some time to figure out how to do it properly, so here is the trick : don't move the camera left and right, put it on a random place every frame, with a max range that you can vary over time to change the strength of the effect. You will see, it gives great result right off the bat !