Indoorlands is a pretty unique game when it comes to building up a theme park and the developer just put up the biggest and most interesting Early Access update yet.
"The indoor park management simulator where you can create your rides from scratch, control them and freely design your halls. Manage, expand and develop your own park to inspire your visitors. Satisfy your visitors' needs by unlocking and researching new buildings, rides, transportation and more!"
With the latest update, they've enabled a new ride editor that had previously been in public experimental testing. This editor allows you to actually build you own ride from parts. This even came with Steam Workshop integration to upload and download creations.
Playing your way is also a lot easier now too, with the introduction of a Sandbox mode that allows you to tweak all sorts of settings like giving infinite money so you can go wild and just build whatever the heck you feel like.
The size of parks has been increased massively too. The game is based on big halls, since the whole idea is that it's all inside in these massive spaces. The amount you can build to place attractions in has gone from 7 to 16 which is huge. On top of that there's also some Christmas themed content, performance improvements and other general upgrades.
You can buy Indoorlands on Steam.