If you're anything like us, the world just seems a wee bit out of whack when things get too quiet on the Lindsay Lohan front. But it looks like all is well: LiLo marked her 18th day under house arrest by throwing a party on the roof of her swanky Venice Beach townhouse. Paparazzi captured the recidivist starlet smoking, laughing and playing with her increasingly marshmallow-hued hair at the get-together, which a source tells TMZ was "very mellow." Lohan, 24, apparently invited people over for a barbecue because "she simply missed hanging out." The group finished off the evening by watching the season premiere of "Keeping Up With the Kardashians." Yeah, Lindsay will surely learn her lesson this time.