Small QOL Update

Just a small update today based on some feedback from the good people over at the /r/playmygame subreddit:

• A sound now plays when you do damage to enemies, making it easier to know that your bullets are making contact with them.
• Similarly, the enemies flash more obviously when taking damage.
• The bullets themselves are brighter and easier to see.

Hope this improves the game even further; let me know what you think!