Nice song :D Unfortunately I had to stop when I got lost in the labyrinth. 

Before that, the combat deserves some improvement: The enemy bullets are too fast and always hits the player so there isn't any way to get good, except by staying far away. You could slow down bullets a lot and add some spread to their direction so that sometimes the enemy can miss the player.

Unfortunately, I feel like this game needs a lot of improvement. Here are a few suggestions.

Only being able to move backwards and forwards really takes away from the movement. I think it would control a lot better if the player could use the W A S D keys to move up, down, left and right.

Ctrl is the key for deploying the shield. The problem with this is that when I press Ctrl to deploy my shield, then press W to move forward, it triggers a shortcut on my computer that exits the game.

The combat would be a lot better if the enemies moved around and maybe even chased you. 

While playing the game I noticed that I could kill the enemies in the first hallway without them fighting back, because I could just stand outside of their attack range and shoot them. 

I hope my feedback helped. Thanks for submitting this game.

Controls require some getting used to, I expect this scheme more for a tank or a car, but I got used to it. Personaly I don't enjoy mazes, but I was able to complete them thanks to walkthrough, although not without difficilties :)

Music at the end is great, IMO it would fit better for the boss fight though :)

Btw. I found out that you can attack with any mouse button, but for some reason only middle mouse button does not produce laser sound effect, while LMB and RMB do. Just something interesting I noticed :)