The window has two panes, one on the left, one on the right. Each has a series of tabs allowing you to select the content you want there. One tab is the system/language documentation. Another tab is an interpreter that you can play the work-in-progress in. Another tab is an interactive index of all the objects in the game. Another tab, if I recall correctly, is a map of the environment you’ve created so far. And of course one tab is the text editor.

It’s free if you want to try it, and available for Mac, Windows, and Linux at inform7.com.

If you’re not familiar with Inform 7, it lets you write text adventures with a language that approximates English. To create a room called the kitchen, you’d write “The kitchen is a room”. To connect another room to it, you write “East of the kitchen is the library”. Click run and the interpreter tab will come up and you’ll have a playable, if boring, two room game.