Super repetitive and grindy. At about 50% the difficulty curve goes out the window and you just have to grind some upgrades to progress. That plus the game being super long and repetitive makes it really hard to enjoy.
There is no reason for so much lag. You are not a AAA title competing on the $3000 gaming computers.
Also if you have edge of the screen deaths dont force people to trial and error there way through a level. Make all the survivable paths visible.