I love the visuals and particle effects in this game. Unfortunately, I can't say the same about other things...
Ok here's my personal opinion about gameplay.
You see, when I launched the game, quickly read a tutorial, played a first 2 minutes... At this point I've seen everything this game has to offer. And to me - it's not enough to continue playing it.
Having replayability is essential for the type of game where your goal is to... gain points. There is no real challenge in your game, you just have to shoot different colors from brushes (I guess makes sense) which apply effects to enemies, or kill them. Also, only yellow or red brush is enough to deal with enemies, I don't think there was any point to add a blue brush, it is not worth using. And about death... There is no indication of when enemy hits me, immidiately after hit game just fades out and I find out I'm dead, it's confusing. A little screenshake when you shoot enemy is a little annoying too. Health bar or multiple hearts would be great to have. A couple of bugs with changing character and player are ok, as long as they're not game-breaking.
About the theme.
It was unclear that I was "altering the games mechanics" until I read it in the description. All I was doing is shooting colors and altering enemies, but certainly not game mechanics... Really, this game has nothing to do with game dev. Even if it seemed like I was changing gameplay - it still wouldn't fit into game dev theme. I'm sure the "game dev" game should be about creating something, doing tasks that are similar to game dev process, like: drawing art, making music, creating levels, tinkering with code, dealing with game dev problems like bugs and errors, etc. There's a lot of things you could think of to match your game to the theme. And yeah, this theme may be really hard if you're making your first game (I assume it is your first game).
So, despite all being said, completing a game is a great experience, especially if you're new in game dev. And it's always good to share it so you could recieve useful feedback. I hope you'll learn from your mistakes and make some cool games in the future, good luck in game development!
Also be sure to rate my game if you haven't https://itch.io/jam/blackthornprod-game-jam-1/rate/319192