Since I’m running an older Mac here at home (too old to dual-boot or run VPC), my knowledge of Portal is limited — and reinterpreted — by the many LEGO creations the game has inspired.
Nevertheless, I recognize a good Weighted Companion Cube when I see one. Le’pena uses mainly Technic and Bionicle pieces to achieve the necessary effect:
i would use clikits dor the hearts.
If you want a free version of portal (albeit not quite the same)
try Portal: Flash version on addictinggames.com!
http://www.addictinggames.com/portalflashversion.html