This one grew on me. First impressions weren't great, mostly due to the menu annoying me a bit (requiring me to select with the keyboard, yet confirm with the mouse?) and how quick and unfair the first death was, since the first enemy gave me no time to react to the fact that it needed two hits.
However, I tried a few more times and warmed up to it. The game feel is quite nice, with punchy sound effects, particles, and a satisfying screen shake. The visuals are basic, yet effective, and although the concept of using health as ammo isn't exactly mind-blowing, the balancing act the healing aura requires is interesting enough to keep things from getting stale.
I do however think it's completely unnecessary for enemies to take two hits. If there were other enemy types with different health values or multiple weapons it could add some extra decision making or variation to the game, but as is it just means you have to click twice as many times (after the initial realisation anyway).
I did have fun, though, and that's what matters.