This was fun and has a good base. It was pretty easy to figure out with a bit of experimenting on the first play, and I was able to win on my second try.

If you are going to have sound settings before the game starts, it would be good to add background music and SFX to the screen. For a SFX slider we usually play one after the value is changed. The menu SFX felt much louder than the combat sounds, and I'd adjust the volumes a bit so the SFX are all closer. I lowered the SFX volume down based on that menu sound, and then the combat sounds were too quiet.

The upgrade screens could use a bit of polish. When I first upgraded my weapon I wasn't sure about the options, since I thought I had a front weapon, but could still purchase a gun there, as well as anything else. I went ahead and got the machine gun for front, and it replaced the current gun that was there. Since it was an upgrade, it would be nice if you got a credit for your existing weapon. The play balance of costs didn't need this, but from a gameplay perspective, it is nice to get credit back for upgrades, even if it is only a portion of the original value. Similarly, it would have been nice to have a warning that your are replacing the weapon. Perhaps change the color of the buttons for mounting points where you already have a weapon and will be replacing it. Disabling the button for purchasing a weapon you already have in a slot would also be nice, unless you changed it so buying more of the same weapon in the same slot allowed for that weapon to be upgraded.

The boss fight was pretty easy. Avoid the things it spawns and try to get close enough to shoot. Certain phases felt like they were all about evasion, though at points I wanted to be able to shoot the spawns. Other phases were pretty easy to get in close and avoid the attacks while hitting back. I like that you give a heads up with the boss telegraphing moves, but it was perhaps a bit too easy. Maybe have the boss spawn some additional enemies, or add something else to mix it up a bit more?

I started with upgrading the front to a  machine gun. Then added a grenade launcher in the rear spot, followed by 2 more machine guns at the sides. I upgraded health, time and damage with what was left over after weapons. Then I upgraded all 3 machine guns to lasers, and that was what I used to win.

Had a ton of fun playing this. 

My suggestions and comments are:

Time over screen took too long each time in between the loop and the upgrade page.

Gem/Heart colors were too similar to enemy colors making it visually confusing. I suggest having gems be unique colors to the ships and have all hearts red. If this is intentional to confuse the player i suggest having the enemies turn into a land mine some of the time so you punish the player for not paying attention to which item defeated enemies drop.

At one point with the mine launcher it caused defeated enemies to spawn gems out of reach from the player up in the air. This also happened once with a heart but it was close enough to be collected.

Maybe have the player kill the remaining spawned in enemies before triggering the boss fight.

Also one question:

If i have the gun set to my forward weapon and i press the gun button again, am i upgrading the gun or just purchasing the same gun over and over? Cause if so i spent a lot of time buying the same weapon over and over again lol.

Great game, I hope you add more boss fights eventually or even mini bosses.

Hey, 
Nice work. I enjoyed playing your game!
I was confused at first with the camera angle, expecting a twin shooter kinda of input but quickly realized (of course!) that this is more of a vampire survivors situation. Overall, it feels like you have a solid game loop and I can see this working alongside a narrative campaign with battles. Two quick observations (to add to those raised): I fell like a visual skills tree can be fun, where you see all unlocked options and can plan a path through the progression towards particular upgrades. Better work on colors might help, for example using opposite colors for pickups and enemies; I feel nailing down the colors is key for these kinds of games. Good luck with your project!

I love the loading screen, it immediately put a smile on my face.

Unfortunately, the power-ups ended up flying through the air and I couldn't collect them.

Improvements (that have not yet been listed)
Counting up the money at the end of the loop and displaying the text is very slow, so I had to wait a long time after my successful rounds :)
The game still lacks a catchy tune, but that should be easy to fix.
Some buttons are positioned above the full-screen button.

Boss level – I'm having performance issues... But that could just be me and my hardware.

Thank you very much for the game. I really enjoyed it.

Its a fun game until you get to the boss.
Since it was my first time getting there  I wasn't sure what to expect.  

I got there with fully equipped with machine guns. The range of this weapon is so small that I mostly played waiting simulator.
Just dodging the boss until he fell  down didn't feel very fun.

Here are a few things I would suggest improving:

• The shop menu: I still dont know if buying a weapon on the same slot does anything. It feels like it does nothing. So why does it steal my money?
• The sound menu in the main menu is kinda useless since you can not hear the sounds you are changing the volume.
• The wave system is a bit weird:
  • The "horse" mob moves too fast in the beginning but after you figure out his range it becomes easy.
  • Haven't really seen the spider mob (or mby i didn't recognized it)
  • The boss feels a bit boring. Mby I chose the wrong weapon but there was nothing to indicate I should get other weapon either.
• Sounds: the mine sound and explosion sound are off if you are using headphones (I thought something feel in my room every time I heard it). Shouldn't use the 2d sound node, just use the normal one, and mby change it to something more intuitive.
• I think you can improve the arena a little bit by making it a colosseum, add a few mobs that look at the show
• Mby even make the mobs bigger than the player to feel like the underdog. 

Good job making the game! I had fun until I got to the boss =).