Nice little game with potential!
The movement of the gun is well managed and follows the mouse well.
To improve it, here are some tracks:
* The spikes are really dangerous! Maybe reduce the collision box a bit
* Don't stay stuck when you jump against a wall, sliding on it would be more pleasant
* I would change the design of the gun, it looks too "realistic" compared to the rest, a little more pixelated and it would go better with the character.
It's a good start, keep going!