This is a really fun bullet hell game (pun intended)! I quite like the fact that the bullets are slow and big, it's unique from other games like this!
I think the game should be a bit harder and have more enemies to give the player an incentive to want to go back and buy upgrades to get stronger. I destroyed the portal and just zoomed through the map and killed everything in my path. I also think the melee weapon should have more range and knockback, so it's a quick way to put distance between you and the enemy
Very well done!