It's pretty difficult, but the game flow is fairly tight, and for a first game this is quite impressive. The soundtracks' fairly basic, but it gets the job done - and this really does harken back to old school arcade games as a result.
The gameplay quickly ramps up on wave 4 in difficulty, and the core mechanic of using enemy projectiles against them is a really cool one. It's a bit rough in places, but the art style and aesthetics all mesh really well with the gameplay, and it makes a fairly cohesive experience overall.
I'd say some VFX for projectile impacts, general juice to really make things pop, and some of the other suggestions like adding bloom or radiance cascades would really make this little treat of a game shine.
I couldn't reach wave ten. But I had a blast getting up to eight.