Thanks guys for all good words!
I've added small update.
For Scirra Arcade now you can use also keyboard keys 1, 2, 3 and 4 instead of clicking the shape. As suggester in the comments on the game page.
press 1 = circle shape
press 2 = square shape
press 3 = triangle shape
press 4 = star shape
I believe it will much easier and fun to play on PC now.