It's a cool idea, but it's incredibly underdeveloped. I wish you had spent less time on reproducing Portal's aesthetic and designing a (admittedly pretty cool looking) player character, and more time on showing off how this idea has legs. 

Also, minor bug report; if the player tries to poof into the wall before it seems like they're "supposed" to (before the button's been pressed and the tutorial messages are done playing) the 3D model won't disappear, but they'll still have the physics interactions of being a shadow.  Doing this allows the player to cross the shadow bridge in human form. 

glitchy but great!

Although it's quite buggy and very short. I do love the concept! I would really love to see you take this further and would even pay for a full game if you polished it up! This reminded me a lot of this youTube video: