Here are a few points that I hope are constructive: the game feels like it’s missing water, since the screenshots show some and in my playthrough my sandcastle slowly crumbles without any visible water around it. This might be a shader bug related to your WebGL version? There’s also an issue with the sound settings UI, which is far too small; making it larger would definitely improve readability.
Other than that, this is a very good jam game that fits the theme perfectly, and it’s also very relaxing. Well done!