A space-shooter! A classic, but mixed with a tower defense mechanic that you cant let any enemies pass? Interesting. Now, at its core, I have no issues with the game, it has a simple mechanic, the goal is clear, its presentation is lacking a bit but works, you even have upgrades! That's some nice stuff.
However, two things make drags the game down a lot. First of; No auto-fire, It quickly gets irritating that I have to spam my mouse-button to fire. It really feels like its a unnecessary task to do, just let me hold down the button please, I don't feel like spamming ads anything to game-play. Secondly, the sounds, especially the explosion effect is very rough on the ears, honestly had to turn off the sound to continue playing.
Other then that we have the small stuff, that I almost always advocate for: Details! Some more visual feed-back on the laser shoot, and taking damage would have been nice (like a flashing sprite or other) etc. the enemies could be a bit more dynamic in how they fly in, instead of always going in a strait line etc. the small stuff makes the game feel less"stiff" and more "alive".
Overall, great job! Its playable and have a soft-spot for pure