Sorry but it means the a button on a video game controller!

You can't even play the game (play button doesn't work, I tried everything, even went through all the keys on my keyboard)

if your using a gamepad A is the start button not the start button if that might help.

For some reason the start button would not work for. Looking at the gameplay video, the game looked really fun. I especially liked the indicator on where you were flinging. Only thing I would change would be to make the game have some more detailed pixel art. Great game!