During the Karaoke session at WPC, Elyot Grant set up an Islands of Insight showcase which explored parts of the game not found in the public demo (including some of IHNN's post-game puzzles, which are ... not easy). I wasn't able to play the public demo because my laptop isn't designed for gaming, so this was my first experience with the game. It's great! I'm very much looking forward to the full release (though I may need to invest in a better machine to play it, oops).
I'm now interested in contributing puzzles to the game, so we'll see how that goes. Here's one puzzle that could conceivably appear within the game, at least from the perspective of the ruleset. It's probably too hard, though.
Rules: Shade some empty cells black so that each number indicates the total count of white cells connected vertically and horizontally to that number including the numbered cell itself. Black cells must form dominos which cannot share an edge, and all white cells must belong to a single connected group. Additionally, no 2×2 subgrid of cells can be entirely unshaded.