[Closed] Designing a kiddy play shed thingy

I have loads of decking and wood, plan to use some of it to build a playhouse for the kids. (Toddler)

We have a large pair of fir trees in the corner and there is actually quite a bit of dead space in the corner behind them. Current plan forming is a little plastic tunnel leading under the tree, with a castle like front, leading to a square room with a table, possibly tempted to build some kind of second level with small windows so they can look out.

Looking for inspiration and other ideas, so post up any pictures of your builds or links to really good sites worth a look