I miss the Refill Energy cards being in the normal pool of cards, honestly. The early game is a lot harder now, and more up to chance.
I had two QoL suggestions;
I think a sound cue when you've recharged 1 energy would be great (maybe even a specific note for 1, 2, 3, and 4 energy, etc.), so you can simply listen for when to fire rather than sometimes needing to flick your eyes down and up to see.
I actually reckon the 'enemy kill' counter in the bottom left and the 'energy level' in the bottom right should swap their visuals. It seems like a number counter for enemies killed makes more sense, as does a recharging circle or bar to indicate how much energy you have at a quick glance. Maybe the 'vessel' could be divided into four sections or quadrants that you can see slowly filling up.