Simple and fun for a little while! I'm personally not a huge fan "trying to get high score" games but it really fits the game jam format.
As the other commenter said, it could use a wave system to be a little more intricate. One thing that could've been cool as well is if the enemy shapes had different weapon types or whatever, but I understand it would've been a bit hard to implement in such a small amount of time.
Otherwise, fun lil game! hope you had fun developing it :)