Most interesting addition in this build is shield mechanic.
Basics are pretty standard -- you hold a button to keep shield active, shield is gradually discharging (you have two seconds or so of shield-time), shield slowly re-charged over time.
Now the interesting part -- deflection. If you activate shield right before enemy projectile is about to hit you, that enemy bullet will be deflected back at him. And you get some energy bonus for that. This is like parry-riposte in Dark Souls :)

Another major change is fuel-explosion -- if you shoot fuel-pickup, it will cause massive explosion (killing everything in pretty large radius). So you shouldn't shoot too carelessly from now on.

And some bug-fixes, these ones caused noticeable slowdown (and crashes) when many enemies were on screen.