This was real fun. I liked the style a lot. Music was cool as well.

Feedback: 

I couldn't access shop when it disappeared from screen.

I'd get stuck on blocks a lot when trying to jump over or on them.

The music would go away when I'd leave tab, until I like collected something. Sounds would stay though.

It would have been nice if there was a dash or run mechanic for faster travel. 

The shop mechanic was great. Everything about it from the slot machine to upgrades.

Loved how I could explore around after the wave to collect coins.

Nice job on adding a sensitivity setting.

I liked the variety of weapons.

The hands never worked for meelee.

Nice stats mechanic.

The bullet hit shot particles would linger on the enemy bodies.

Nice increase in difficulty over waves.

Good variety of enemies.

Overall, nice job!

I have not been able to stop playing it. It is a very fun game. I stop playing it to send you this comment, but I'm going to continue with it for a while hahaha.

I’m not sure if it’s just the web client, but I had some problems with shooting working. It seemed as though there was a timer on how fast I could shoot or something like that. Overall, I think there’s a lot of games like this, and it might be hard to stand out from the rest just because it’s christmas themed.

I would suggest perhaps speeding up character and enemy movements and projectiles. For example, the enemy that shoots a skull at you is too easy to dodge. Also, the UI looks a lot like a mobile game, which if that’s what you’re going for then great. If you are primarily targeting desktop users then maybe make it more simple or maybe more keyboard friendly.

I do think the modifiers from the slot machine are a good idea, and the values seem right.