Hi NiHuShu ! Our games are really similar, we almost did the same projet to be honest. I think we can both take the best out of the other project to polish them.
What you might improve is the usage of you're screen space for the character movements. Here's what I mean: I did the same movements again and again to beat the waves and did not use all the space you left me with. You could force the player to change his position by spawning mobs near him, forcing him to update his position constantly instead of "camping".
One last small point. In our game, the player has the opportunity to chose an upgrade after each level. Where your game force him to collect coins (which is good) to take one. Here's the thing, players that pass all the levels but doesn't collect coins won't get any upgrade. Which can be frustrating since you are not getting any reward for your progression.
Here's the link of my game : https://itch.io/jam/gmtk-2019/rate/463391