Here is the contents of a desktop file created by steam:
So, if you know the game's id, you just need to call/start steam like this:Code:[Desktop Entry]
Name=World of Goo
GenericName=Steam game
Comment=Play this game
Exec=steam steam://rungameid/22000
Icon=steam_icon_22000
Terminal=false
Type=Application
Categories=Game;
Hope that helps.Code:steam steam://rungameid/<game's_id>