I really like the menu at the start! I do wish that there was more incentive to attack the enemies. Maybe you could be defending something at the bottom of the screen? Maybe you get bonus points for every enemy you defeat? Just a couple of ideas :)
Also worth noting: it seemed like I wasn't able to attack after awhile, the attack button would just stop working after some time. I don't know if you have some kind of limited-ammo gimmick, or if it's just a bug in your code.