cool concept here are my thoughts:
-some people won't know there are more features so i advice to make like a tap but with the requirements to unlock or ???
-game is a bit short and killing the first guy is really repetitive
-clean Ui good for the eye
- i think it would be cool if i have an hp bar too once it's there there is a cooldown until i get back my health then i can resume attack the monster so i just don't sit and click same button
- also i think it may be nice if there is a shop to purchase more upgrade like multipliers and such
rating 8.5/10 for concept but short on content