I like the mechanic where you have to click on ammo to use it (and when enemies drop their unique ammo), though sometimes I wish I had a powerup to expand my radius, or reach for clicking stuff. The premise that everything wants a bite of you is pretty silly, lol. I will say though, that most powerups don't feel like they equip you properly for dealing with the hordes of enemies. An example is the more power upgrade- even when choosing it four times, it oftentimes takes more than 3-4 ammunition to deal with a single enemy, and even then- by the time you deal with that single enemy, I kid you not, 50 more start to follow you. I tried various combinations involving the star, pierce, the one that makes you speed up, the slime, more ammo drop, so on and so forth, but I still felt like I lacked power. I stopped playing when the green crystal one tapped me (lol)
Aside from that, I really like the ability to use the special ammo dropped by enemies! With each enemy projectile having a special effect, and buffs to many upgrades, I think this would be a wonderful survivor game I would be more than happy to revisit. I was also fond of the enemy variation, it would be cool if some of the enemies did different things.