Hey, this concept is really cool! Before you start releasing it, however, I'd recommend giving the player a clearer idea of what the objectives are, and decreasing the spawn rate of both types of atoms. This way, I think it would feel a little more structured, and probably make it more challenging to gain points than simply waiting for a ton of white atoms to spawn.

Neat little game, I think if i were to suggest something, it would be to add more progression or content of sorts, as i noticed after a few minutes, not a whole lot changed, so perhaps more enemies or level types, or things of that nature, maybe even an auto upgrading system so you feel like you're becoming more powerful, but otherwise, as a prototype type game, it's pretty good

Not bad for a demo. Nice arcade-like game mechanic.
The fire rate , amount of enemies, and movement make for a balanced challenge.
Add a better looking art style, music and a scoreboard, and you'll have a pretty decent game.