smealum from GBATemp has been working on a version of Portal for the DS, here is a quote from his thread, along with some video:
ok so basically I’ve been working on this portal adaptation for a few months now. it’s coming along quite well I think so I decided it was time to give it its own thread. the game is being programmed by me and the graphics are being made by Lobo.the idea is for us to make an original campaign featuring none other than doug rattman as a protagonist. the game will also feature a full-fledged on-board level editor similar to the one found in portal 2’s perpetual testing initiative, so my hope is people will make their own puzzles and give the game some replayability.features so far :– working portals (you can place them, look through them, go through them)– okay player physics (for instance, momentum is conserved when going through a portal, flinging works great)– a full fledged rigid body physics engine for turrets, cubes and stuff (watch the video, I think it’s pretty cool for a DS game)– mini gravity gun !– an on-board and intuitive level editor– more or less working puzzle elements (including buttons, dispensers, turrets, energy ball things, doors, emancipation grids…)– an entirely new gameplay mechanic ! (not fully implemented yet but I think it’s going to be pretty neat)
For more information, check his thread here.