-Candles make no sense for a sci-fi setting, and weren't a very good mechanic in Castlevania in the first place.
-I don't understand why there are "pets" hidden inside the candles or why they're used as currency.
-Juding by the videos you posted, it looked like it had the worst jumping physics imaginable. You really need a particle effect to make it clear that you have a jetpack.
-Make the flight time limited (but still generous) and have it recharge while on the ground to give the player a reason to not stay in the air all the time.
-When on the ground, the character should jump before activating the jetpack, and you should be able to jump without using the jetpack by tapping up.
-Gravity stops working when you fly into walls.
-You should be able to shoot crates to open them.
-Don't hide enemies in crates.
-Hits don't register if the muzzle is less than 3 pixels away from a target.
-I hate the short range on the gun. Feels really unsatisfying.
-The axe feels almost mandatory. It's pretty much a game over if you lose it. Laser needs to go through walls.
-Spawners are too fast for how cramped the levels are.
-Needs continues, especially for testing.