What an amazing game!
What I liked
The game concept is art and I love the zen mode. I love that it is also a two player coop game :) even if that might not be intended. The harmonics play out the shanty very well and without the pressure of the time limit it is really an relaxing and fun experience. Given that it is so minimalistic, a lot of effort seems to have been put into making the overall cardboard look very smooth and nice. Indeed one of the best entries so far!
Other thoughts:
The "survival" part on top of the game feels more contradictory than helpful here. The game itself is great but it suffers from the theme a bit. The mechanic induces stress while the sound is soothing. That made me switch to Zen mode very quickly because it just felt a bit odd.
Overall:
Very polished entry with a great concept and great execution. Definitely in my favorite list now.
Keep it up and thanks for submitting such a good game!