I had a look at your game. I like the overall idea because the idea of killing hoards of zombies never fails to entertain! A few things I think you should focus on improving, I won't sugar coat it I'll just tell you exactly how I feel about your game so if I sound harsh I'm just trying to tell you what I think needs improving so your game can be the best it can be:
1. The art. Not trying to sound too harsh but right from the start it wasn't the best. The text was low quality which I assume is maybe some kind of stretching issue, I'm not too sure. Then in the actual game the art feels way too in your face, with animated stuff everywhere that almost looks like GIFs, and I'm not really sure what the purpose of those are. I can see the pixel art style that you're going for but it looks a bit too much like an amalgamation of assets off different websites that are stretched/resized which deteriorates the quality. To fix this I'd just say to you, look up tutorials for importing/resizing images in phaser (assuming it's made with phaser, said that on the game page) and also there isn't an issue with using online assets, but I'd try a bit harder to find a style and stick to it.
2. Gameplay. (sorry if this sounds too harsh, I'm really just trying to articulate myself so you can understand from my point of view what I think needs improving).First off, it feels very clunky, the hitboxes feel wonky, buttons and controls don't feel very responsive. If you're new to game dev I would say just keep making games or keep working on this one, you'll improve with time and learn how to code more and more efficiently as time passes. If you really want to get your skills up quickly, look up tutorials for phaser/whatever you use and try to rewrite your code a bit to be smoother.
3. Sound, sound is probably the thing that needs the least work, I think it's alright but the fly sounds are actually quite off-putting and annoying and if you think about it, it doesn't really suit an action game even if it suits the environment.
4. Difficulty/playability. I found the difficulty ok, I would introduce enemies a little bit slower though for players to get used to the game and how it feels, and I would also make some kind of interactive tutorial as well because that really helps to introduce players to the game.
Anyway, this is a great start and I look forward to seeing how it improves! Also, would you mind giving some feedback on my game Slugger? I've just rewritten the foundation of it in a new engine and it would be great to get some feedback on how it feels so far.