Love the different messages when hovering over the start button. The sound effects when enemies are destroyed is incredibly satisfying to listen to, especially when you kill a bunch of enemies at once.
The upgrades are very straightforward and have actual weight, which makes getting an upgrade feel like an actual reward!
One of my favorite parts of the game was the sense of humor, which it is full of. It's a very charming game that plays really well and is simple to understand. This is a very strong first game. I like it!