Number counter - key press goes up 1 number Options

[TheMonDon]

Hello, I would like to make a "counter", with say a colored background and big, bold black numbers in the center of the page.
I'd like to be able to press a key, say "X" to go up a number, each press would go up another number.
So when I press X and it's on number 5, it goes to 6, and so on.

Thanks.