Hoo boy.  Lots of thoughts playing this.

First off, the good.  The opening cinematic is excellent, feels like something straight out of the Genesis era, which is not a bad thing.  Background graphics and enemy design is also pretty good, could use a bit of polish and animation to really make it stand out but the look is fine.

Next, the horrible.  GET RID OF THAT TUTORIAL.  I don't need a forced 2 minute practice room where all of the controls are locked except the ones I'm "supposed" to use to understand "WASD to move, left click to shoot, right click to use special weapons, middle click to use bombs."  I expect a lot of players will quit right there.  Either make a single popup screen to explain the controls, or if you want to be really fancy make them pop up on screen during the first level when you encounter appropriate enemies.  

Okay, now on to the gameplay itself.  It took me about until the third level to understand what you were going for, up until that point I figured it was just a terrible game where the enemies had way too much health.  It feels like you're going for a sort of "bullet hell" gauntlet of fights where you have to defeat each "wave" of enemies before you can advance, and you have a bunch of special weapons with different effects to deal with them.  Almost like an RPG series of battles.  This is an interesting concept!

Unfortunately, with a few exceptions, the execution is bad.  Most fights are extremely boring.  When you're just sitting there shooting at a randomly-placed bunch of enemies that take way too many hits to defeat, and the enemies just sit there and shoot straight ahead, there is no real challenge, you just have to position yourself in the right spot, then shoot a bunch of times.  There are also a bunch of times when several enemies are placed on top of each other, and they have a continuous beam of bullets.  In this case it is practically impossible to shoot them without being hit, and also it looks ugly.

The first thing you should do is come up with a system for placing enemies deliberately, instead of randomly.  Use fewer enemies, but plan out each wave in ways that will present interesting challenges, don't just throw a bunch of bullet sponges at the player.  At least do something to stop them from being spawned in clumps.  I know it's the easy way to make a shooting game but it's lazy and feels bad.

The game could also use some more interesting enemy behaviors.  Make some of them actually move, and fire in different patterns (there are a few, but most just shoot straight ahead).  Some can even interact with each other, like maybe some could generate shields to protect their allies, so you have to hit those first.  Plan out each encounter carefully, and you could have some very interesting situations for the player to deal with.

Another interesting thought that might work for a game like this - give each battle a time limit, after which the enemies pass, and reward the player with upgrades for defeating them before they escape.  This way, mastering the early parts of the game could make the player more equipped to deal with the harder parts later.

This game has potential!  It's bad right now, but with improvement it could be a lot better.