This could really use a lot of improvements.
More enemy types, level selection, upgrades, bosses and so on, be creative.
Not to mention it needs easier-to-use controls. WASD to move and mouse to aim and click to shoot would not be a bad idea, and make it so that you don't need to press a button (or click) repeatedly to fire.
(I made a similar game to this so I know how it CAN be better)
If you can make this, you should be able to make games so much better than this, you just need to be creative.