You may know that for one of my hacks, I had an idea for a Windows Zone based on the Windows OS. Unfortunately I lack the level design skills to make that work.
So instead, I went the other way, and implemented a decent imitation of the Sonic engine in VB.NET, and made it able to interact with all the windows you have open.
So here's the current version of <a href="http://x-hax.cultnet.net/MainMemory/WindowsZone/WindowsZone.7z" target="_blank">WindowsZone</a>, and here's the <a href="http://x-hax.cultnet.net/MainMemory/WindowsZone/SonicEdit.7z" target="_blank">Animation editor</a>.
You'll also need the <a href="http://www.microsoft.com/downloads/details.aspx?displaylang=en&FamilyID=0cef8180-e94a-4f56-b157-5ab8109cb4f5" target="_blank">DirectX Runtimes</a> if you don't have them.
<!--coloro:red--><span style="color:red"><!--/coloro-->Note: if your entire screen turns magenta, you'll need to switch your color mode to 24-bit or less. This is a bug with GDI+ and I don't think I can fix it.<!--colorc--></span><!--/colorc-->
Can collide with the inside and outside borders of open windows.
Physics values based on the [Sonic Physics Guide], multiplied by 4 in most cases.
Sound Effects that somebody else ripped from S3K
Animations from S3K ripped with SonMapEd, aligned and timed by me
Can pick Sonic up with the mouse and move him
Useless looking up animation
Useless ducking animation
Sonic can Roll, Jump and Spindash (Spacebar = jump)
Uses braking animation if you have enough speed
Menu available by right-clicking Sonic's icon in the system tray
Can choose which boundaries are solid for windows
Can choose what happens when he reaches the edge of the screen area: Wrap, Stop, Ignore
Can go up off the top of the screen indefinitely
Dies when he hits the bottom of the screen
Uses pushing animation when pressing against a wall
Adjustable framerate (defaults to 16ms ~ 60fps)
Can show collision boundaries (red for windows, green for Sonic)
Has customizable physics and animations, by editing or copying sonic.ini
Objects other than Sonic (springs etc.) this will likely mean you won't be able to stand inside of windows anymore
Feel free to suggest improvements or new features.
I may take this and make a more normal fangame engine out of it, but I'd need to rework collision some to get slopes to work.