Not bad. Nice graphics, nice music, somewhat addictive gameplay...I'm mostly just surprised that you're allowed functioning metals in a under-judgement game.
At any rate, I suggest adding in either some form of story, or something by way of either an upgrade system (draw inspiration from 'Upgrade Complete' or other games), or a score board at minimum. In addition, for an 'achievements base arcade game', there aren't any actual in-game achievements, so maybe add those in as well instead of relying soley on newgrounds achievements (especially if you put this on other sites, like Armor Games. Kongregate has achievements though, so...it depends)
Keep on keeping on.