YEs Redaria I have been to Happy Valley in Beijing. It's actually really fun. I've been to the top three if not thee biggest and one of the best amusement parks in the world before. I got to go to Magic Mountain near Ventura County in California. I know it was the top three biggest amusement park and it might have been thee biggest amusement park in the world but not too sure on that. In comparison to that theme park I would say it does have significantly fewer rides than a Magic Mountain but it still has enough rides for you to have fun in an entire day. They also have people dressed up and they have some sort of haunted house there which is really fun. They have the drop which just goes all the way up and you can see nearly the entire theme park then it drops you down. You can find those games to win prizes too so it's a lot of fun! 

Yup.. Great place. Lots of rides and activities. Rollercoasters are amazing too.
Just make sure you go there on a weekday. Queues can be unbelievably long.

if there is no happy valley in your heart so going to happy valley is scar.

I heard the happy valley in Shanghai isnt very happy.  I've never been but it looks crap and dirty