If you actually want this to be a semi-serious game, you need to: make some overhead(shop costs, advertisement costs, parts costs, research costs, etc.); fix the sound buttons(combine them and make it not go to the main menu when you turn it back on); make the main menu stop the game; make the sales less erratic; make it possible to go between the gun making screen and the store without changing your gun; let you discard changes to your gun; maybe let you sell more than one type of gun; and get rid of the custom cursor.
If you actually want this to be a semi-serious game, you need to: make some overhead(shop costs, advertisement costs, parts cost, research cots, etc.); fix the sound buttons(combine them and make it not go to the main menu when you turn it back on); make the Main Menu stop the game; make the sales less erratic; and get rid of the custom cursor.
I would have rated it 4/5, but there are a few things that are just really annoying and bad. The difficulty's good, but I found myself losing a lot because I held a button down a little too late because of lag and it'd count it wrong for every frame ending up in me losing in a second if I didn't notice. Lag itself is another big problem that I had because I couldn't adjust the quality. I'd lose several notes or push some wrong because of it. Then I also had to start over two-thirds of the way through because I wanted to configure my keys. Overall, I had a rather negative experience because of these and rated 2/5.