Thank you, please be nitpicky :)!
Very good valid feedback, I definiely agree on that restart should let you replay instantly, it was just forgotten, but should definitely be changed to restart the "game-level" instead of taking you to the menu!
The purpose of the countdown was to build anticipation before the game starts. It might be too long, another idea could be to make it skippable by clicking.
Thank you for your feedback!