This game is designed to showcase the Elm Narrative engine. Although it's not the first game written in the engine, it's the first I've seen.
This engine is based on the Elm programming language. From what I've seen of the engine, it features less emphasis on branching and more on context-sensitive choices (which would be useful for inventories and such).
In-game, the same link can have multiple effects depending on when you click them. Because the links can scroll out of view, there is a handy top bar listing all active links. This gives an experience somewhere between Twine and Robin Johnson's Versificator engine (which the author praises in an early dev blog).
There was one critical issue that cause me trouble. Due to the large font size, I usually had to rely on the bar, and the bar wasn't always there. I had to tap the up arrow to make it appear. This was the case in both Chrome and Firefox. I know this is just an option in the engine, as the other sample games use a constant menu bar.
Everything else about the engine was smooth and enjoyable. I could see this engine gaining wider adoption.
As for the game itself, it is a metaphorical game about the pursuit of light and darkness. It's short, contemplative, and even melodic at times. I had difficulty making an emotional connection, though, which may be related to my interface frustration.