V2.51 posted - rendering fixes

I've posted an update to the game after some late-night bug swatting.

• Fixed a problem with alt-tab causing crashes and freezing

• Fixed problem that was preventing launch in Windowed mode

• Added Borderless Window option to launch menu

• Tutorial video now runs in a Pad Hopper level, not an external website. This tutorial level is not 100% complete but I wanted to get it changed asap.

• Swapped out some shaders that were causing trouble with DirectX11

Thanks to Deozaan for help with troubleshooting and testing. Thanks also to ThreeSon, MrHanMan, and plyr1739 for reporting the bugs. Can't fix 'em if I don't know about em. ːsnaggletoothː