I have created a simple game that you can download, play with and submit to the store – both to Windows Store and Windows Phone Store – reching millions of users world wide. It contains the basic functionality of a 2d sidescrolling shooter game.
This game starts simple, then after level 3 – more enemies will come, and after level 4 there is a possibility that a harder enemy that takes two shots to kill will spawn.
The game supports input of touch, mouse, keyboard and the xbox controller (just connect it to a surce or a computer and play!).
This game is pretty simple, but with your modifications to it, it can be a totally new game with much more content.
Open the game in Windows Store (is soon published)
Open the game in Windows Phone Store
Download
You can download the entire Unity game starter kit here:
http://sdrv.ms/1aE3qfN (~170 mb)
What can I do?
You can open the project using the free or pro version of Unity , modify the game by
adding more enemies, bosses, weapons, power ups, character attributes so when
you level up you can get more strength, shoot quicker, move quicker ++, add a
world map, create levels with different landscapes, add two-player, make it 3d –
it’s all up to you, and it’s really simple using Unity! 
Changing the GFX
The graphics are taken from http://wootstudio.ca/win8platstarter and the entire eninge is based on this so simply replace the GFX in this starter kit with these to change the graphics (might need to do some cut/paste on some power ups and building), but the character animations and enemies are just a file-replace away from getting changed.
You can also modify these files with your own GFX, or rewrite the routines so it loads your own files the way you want.
These packs are awesome and contains good and cool GFX free of charge!
Exporting your game to Windows Store and Windows Phone Store
The pack comes with a game that supports both Windows 8 apps and Windows Phone 8 apps. If you make modifications, just export it from Unity (replace the folder that is named Windows8 for Windows Store apps and WindowsPhone8 for Windows Phone Store apps):
But don’t delete these, or export to another folder – these folders contains code that handles important Windows Store and Windows Phone Store tasks such as Fast App Resume and Snap View. When exporting from Unity, it will only export the files that are new – so this code will not be overwritten.
In Unity just click File->Build Settings, select Windows Store Apps of
Windows Phone 8 as the platform and click Build. 
Then, you will be asekd where you want to export, select the folder (Windows8 for Windows Store Apps and WindowsPhone8 for Windows Phone 8) and click Select Folder:
The app is now exporting, and when done – open it in Visual Studio (free to download here:http://www.visualstudio.com ) and do the process for submitting the app to the store (build it, send it through the WACK to build and test the app packages locally and then submit it to store).
More information:
- How to publish to Windows Store
- How to publish to Windows Phone Store
Step by step tutorial on how to create this game
I have created a five part tutorial series (it’s a part of a longer Unity for Windows tutorial series) that will create this game using Unity:
Sound effects and licensing
The sound effects used in this game is licenced based on the Creative Commons Attribution 3.0. If you redistribute them, use them or publish this game, make sure you follow the guidelines here: http://creativecommons.org/licenses/by/3.0/
The SFX is downloaded from the awesome site http://soundbible.com