Where you write your Mini App's code, compile it, and test it in the simulator.
The workspace has your project files on the left, the code editor in the middle, the simulator on the right, and Devtools at the bottom.

Use Editor, Devtools and Simulator in the top left corner to show or hide each panel.
The simulator runs your Mini App as it will look on a phone. Pick a device from the list above it — for example iPhone 5, iPhone X or Nexus 6 — or choose customize to set your own size.
Click Compile to build your code and reload it in the simulator. Ordinary Compilation opens your Mini App on its home page.
To test a page directly, open the compilation list next to Compile and click Add Compilation Mode.

pages/index/index.key=value&color=black.Click Confirm. Your new mode appears in the list, and Compile opens the Mini App on that page with those parameters. How a page reads its parameters is explained in Routing & query.

The Devtools panel has these tabs: