What a fantastic idea for the theme! Really loved the simplicity of it despite it being quite tricky. It was a bit confusing at first when you show how to handle multiple keys at once, I thought that whenever multiple keys were shown falling then all would fall down if you lift any key. But playing the last level it seems that lifting up a key only makes all the other falling keys fall down faster for a bit. Maybe a slightly different explanation would've been better but this is a minor gripe.
Great job on your first game jam, I wish my first one was as good as this! :)