You turned Space Invaders into a button masher, the gameplay is too "flat" right now, enemies all move at the same speed and fire at the same rate and never change. You can easily clear whole rows of enemies simply by standing still, spamming the shoot button and dodging the occasional bullet, there's no strategy involved like in the original Space Invaders where you practically dance with the aliens, hiding behind the barrier and then peeking out when your weapon has reloaded.
It's odd how enemies keep appearing, I already cleared the whole screen but I have to wait the next row of enemies to show up.
Some bullets seem to hit multiple enemies sometimes, I don't know if it's just the hit sound playing more than once though. The audio as a whole is WAY TOO LOUD too, at least 3x louder than it should be.
I don't know what you're planning for this game but if you want to make a Space Invaders clone then you should look into what made Space Invaders fun.