This is the original experiment, precursor to Tiamblia
You can play around with it here. There's no default world, so you'll have to press E to enter editing mode and draw polygons to create some terrain. Right click to delete a terrain polygon. Place some trees by selecting Tree from the Entities bar and clicking where you want the bases of some trees to be.
Use the arrow keys or WASD to move, down to mount/unmount a steed. Press F to fly.