There's definitely an interesting setup here, and a nice upgrade system, though it didn't really feel like a skill tree it definitely was cool to upgrade a few of the stats and the skills. Though it did take me a second since there were no visuals to read the entire tooltip of both the skills and the upgrades. After that though I definitely abused it to go as crazy as I could. Which was awesome.
The only issue I'd say for me with the game overall is the fact that it's click to move combined with click to shoot a specific direction. Which leads to a lot of conflicting controls, especially if we're talking a bullet hell setting where you REALLY need to dodge those bullets if you don't wanna die. So personally I'd say putting movement as an option for WASD would be nice, otherwise though there's some interesitgng enemy variants and some cool visuals to back it up so just some more gameplay polish I'd say.
A big addition I would personally recommend would be some sort of variation on the attacks, something more than a wider shotgun spread etc.. Definitely interested to see if this game goes anywhere tho.