Homebrew modder “Smealum” has done something amazing with the DS. Although not close to completion or even playable, a running adaption of Portal is running on the system. Work on the project has been taking place for the past six months or so.
Smealum notes of the video:
“This is still extremely early footage so please don’t be too harsh. Lots of debug features are present, including the ability to fly, see portals through walls and move cubes from a distance. Also, keep in mind this was shot in an emulator which provides good but still less than perfect rendering. As such, be aware that most (not all, but still) of the graphical glitches you can see in this video don’t happen on hardware (mostly the portal transition is a lot nicer on an actual DS).”