Interesting game, got the basis of a wave-based shooter with no bugs I could find so good job! For a 1 person project I can understand that it it is hard to expand too much on an idea. There are a lot of things that could be added e.g. upgrades system, new enemy types but I think the absence of these is more likely due to lack of time than anything else. The best way to learn is through practice so good job for entering a game jam as in my experience that's how I learn the most!
Also there was lag spikes when new objects were seen for the first time, you can fix this by using PRELOAD instead of LOAD ;)