Bitsy is a free online in-browser game creation tool, particularly tailored for creating small interactive narrative games and worlds, with the emphasis of walking around and talking to people and creatures. The tool allows for editing of sprites, colours and dialog, along with some simple scripting.

The tool itself is quite limited, but is really great to sketch out a game idea quickly. If you find the engine ultimately too limited for your game, there are lots of third party tools you can use which add more options to your game.