A lovely concept ;)
It's such a simple concept, and it still plays very well.
A few minor tweaks should be considered though.
The choice of colours aren't exactly eye-catching. Try to liven the game up.
Maybe a lives system wouldn't be a bad idea.
Give a second option to the user, where they can choose what difficulty they want their game to be throughout.
Well, that's all I can think about now. Good luck with all your future projects ;).