This game is lots of fun for such a simple concept. Here is a brief summary of what I like and dislike about it
What I like:
1. The art style is simplistic but does its job very well. Everything is clear to the player
2. The gameplay is quite accessible. The controls are intuitive and not that complicated
3. The gameplay loop is fun and I think you can have a decent amount of hours playing this before it starts to get old
4. The music is a good fit for the game
What I don't like:
1. There's very little feedback to notify the player that they've been hit. I found myself having to constantly check how much health I've got because I didn't even know when an enemy bullet hit me. The feedback is very subtle and could've used some damaged overlay and a sound effect, but probably no screen shake since there's a lot going on in the game already
2. A leaderboard would've been nice so I can compare my performance to that of other players, but this probably wasn't feasible due to time restrictions, so I understand
3. The yellow enemy bullets can look a bit similar to the coins, which leads to me not realizing that these are bullets and I need to dodge them instead of collect them :P
Overall, nicely done! I really loved this game