This morning, my first Windows Phone 8 app was approved and is now available in the Windows Phone store. You can download and install it on your phone from here or search for "MathFlashGame" in the store.
The game simulates arithmetic flash cards, displaying an addition, subtraction, or multiplication problem. The user supplies the answer and the game tells him if that answer is correct. You have the option of limiting the operators and the range of numbers displayed.
I began the app about 4 weeks ago as a learning exercise. Not only have I never written a mobile application, but I have very little experience with XAML. Everything was new to me, from the data binding to local storage to the mechanism for responding to a change in phone orientation.
I learned a lot on this project and I am inspired to write more applications for this platform. The experience was fun. If you are considering writing a Windows Phone app, I encourage you to take the plunge. There are a lot of helpful resources online and the cost for a developers license is currently very low (only $19).
And if you have a chance, please check out my app and let me know what you think.