Thanks, I had fun with this one. I think it has potential.
The level is randomly generated but I made a helper function for the spawner.
I used Vectors (X, Y) because it's an easy way to expose two linked float values to the editor.
X is spawn frequency in seconds, Y is how long that 'phase' is active.
All the code is on GitHub, too. https://github.com/Falconerd/30-games-30-days/
This is game 17.