So gosh darn cool. It reminds me of the endless hours I poured into RPG Maker years ago.
To have this power in the browser and be able to export a working game feels bananas. I know how Moore's law has progressed, how the power from behind our browsers was many multiple times more powerful than the Game Boy Advanced, but it still feels like it shouldn't be possible.
Oh the wonders of technological progress.
Edit: I got a bit ahead of myself. You can export and play your game in the browser, but you'll need to download the editor to create a game. Good news is the application is cross-platform and includes Linux for us super dorks.