Definitely change the font color from black to something brighter like white or similar; right now it's kinda hard to read since it's on such a dark background
The visual feedback from hitting enemies is done pretty well, but the audio side still needs some tuning I think; maybe just make the sound effects a little louder so it's more satisfying and you really feel your character putting damage into all the stuff that's flying towards you on-screen
And when the tanks flash from taking damage, the whole thing should probably flash, not just the base, right? It makes sense for the boss that just the guns flash so you know which part you're hitting, but for just the normal tanks it'd probably look better if the whole entity flashed white and not just the base
Really nice use of effects though on the bullets/power-ups, though ; there's a surprising amount of polish in that regard