I don't think there is anything wrong with this game, but I do miss some powerups or something.
As you're saying, it's an early build of this game which is gonna be a bullethell. Could see great potential in this game.
Would love to see other characters with other spaceships that shoots differentially than Sputnik 1 or something like that.
Not too hard so I like it :)

I like the sputnik character design but perhaps work on the difficulty of each stage and enemy patterns a bit more. perhaps power ups and other characters? none the less good concept.

It's a start. But there are some glaring issues. Your hitbox is ridiculously large making some of the patterns impossible to dodge, and the slow firing speed and slow bullet speed make it very difficult to hit anything.

I do like the idea of a shmup where you have to carefully aim your shots (that's very uncommon in shmups) but if that's the case then the bullets should travel a lot faster so it's easier to hit stuff.