Fly Fishing

I didn't get to play this. One of my friends said that it felt more like flying rather than swinging. And I can see how tweaking the physics to feel more like swing might create a game-play that is slightly different but feel interesting to play... (I guess there's rather something unspecified around movement and physics where my intuition is tingling that there could be some or other tweaks that could make it feel even nicer or maybe have a more direct sense of challenge or pacing. Sorry for being vague.)

In a way I think this game feels a bit too minimalistic, particularly with it mainly being whitebox geometry in space. But I also think you are thinking right in making the lighting do the heavy work! Shifting the sky color, especially if reflected well on the geometry keeps things interesting. 

Some form of uneven geometry in the background, like a set of static clouds or star constellations could enhance the players sense of direction when looking around. any form of spatially distributed particles might also add with similar effect.

I also believe that just something on the line of boid-like sets of fish could be a small intervention with massive results. (Easy for me to say it's simple, lol.) The fish can swim alongside player (move in same direction when close) and disperse as you get very close, etc. Then I think you would approximate similar factors that makes for example the game Journey visually and interactively so appealing.

Hope Gotland Game sees the potential in this project embraces procedural generation more, as well as the Godot engine!