If you are new to Arduino have a look at this to get started:

How to have fun with Arduino

Code attached and on GitHub below:

Code on GitHub - this has the most up to date code including Art work and Sound!

There is still a lot to be done with the code, see below:

High score functionality.

[Done] Better key pad control code.

Decent random number generator.

[Done] Start thinking about adding sound.

Create a letter font, create a proper system for rendering numbers and letters.

Tidy up code and optimize for memory, sort out the globals and types.

Create defines for all the magic numbers but they are useful for now.