You're worried about throwing a fun party for your kid's birthday. You want everyone to have a good time, but you don't want to spend the weeks to come picking cake frosting out of the carpet. Fret no more. Bladium, located in a huge converted hangar on the old Alameda Point naval base, is your ticket. The staff there understands birthday parties and will do everything in their power to make things go smoothly. Whether it's roller hockey, volleyball, soccer, or basketball, the Bladium folks put on the party for you. For $195 to $230 (depending on whether you're a member) you get pizza, soda, and chips for up to fifteen kids. Just bring your own cake and the rest is done for you. A young staffer shows the youthful horde how to play the game of its choosing and then lets them go at it with plenty of encouragement from the peanut gallery. (There's also a fun play area for younger siblings too small to take part in the action.) The adults are welcome to join in or take a much-needed rest and watch on the sidelines. Following the sporting action, the kids gobble their snacks and it's all over for another year. And you go home with happy, exhausted kids to a nice clean house.