This was really well done for your first game ever, seriously. The sound design was balanced nicely, and it was fun to play. The background looked good, and the color palette worked well. It didn't interfere with enemy bullet readability at all. The boss fight you added was fun too, especially as a surprise once the score got high enough. The enemy explosion animations looked good as well. Also, nice job getting a few difficulty modes in there. Balancing three different modes is not easy. Really nice job, especially for a first game. Hope you keep making more.