This game has some good qualities but several severe flaws.
- Unique and fresh story
- Good graphics
- Good music
- Relies on the "just spam everything" technique of lazy game design
- Starts to lag at higher levels or with higher upgrades
- It's really hard to tell what's good and what's bad. Your shots aren't really distinguishable from those of the enemy as well as collectibles just being all over the place and the lag kicking in and, yeah, not a good combo.
- Final boss really needs to not hog the bottom of the screen (and thus invincible) like 98% of the time, especially with how much you need to grind here anyway.
- Very grind-based gameplay
Consider toning it down for future web-based SHMUPs. It's better to require a bit of strategy rather than just spam everything at the player and require the player to spam back in return. SHMUPs aren't a great genre for web-based games *anyway* but if you're going to do one do it right.
Hint: It's probably not a good idea to have so many collectibles in SHMUPs anyway as they're already going to tend to push the hardware limits as-is, so you'll want to do everything you can to reduce resource usage. Powerups are fine. Screen littering with collectibles isn't. You especially want to keep the amount of objects (and the effects on those objects) to a minimum when you're doing something like a SHMUP, which generally requires tons of objects on-screen anyway.