They are offering the game for FREE (for a week) and in turn they ask that you upvote the game on Steam Greenlight. However, you won't receive a Steam key for when the game is released on Steam.
Vote here - http://steamcommunity.com/sharedfiles/filedetails/?id=100398…
Direct download link - download.headupgames.com/downloads/BridgeConstructor_install_v1_2.zip
Normally $10 on Gamersgate - http://www.gamersgate.com/DD-BC/bridge-constructor
Wondering if it is not against the Steam terms to incentivise upvoting in greenlight.