Thank you for the comments!!!
Yeah I didn't really have much time to make a dedicated mechanic so I just went for a very simple shield system. In hindsight it would have been better to make the golem a short-lived hyper mode like what WBaWC did.
The scoring strategy is to regularly switch between using your normal shot (to raise gold value) and using golem (to cash in on the gold value), but it makes the game ridiculously easy for survival indeed. Honestly I want to pull a CAVE one day and make extends super hard to get to offset it a bit haha