Feels like anything can happen with coded puzzles… Here’s one that’s probably of medium difficulty as far as coded corals go, though the puzzle type seems to be inherently difficult.

Rules Map the letters to distinct positive numbers, and solve the resulting Coral puzzle: Shade some cells, such that all shaded cells are connected by edge, such that no 2-by-2-square is fully shaded, and such that all unshaded cells are connected to the puzzle border by edge. For clued rows and columns, the clues give the lengths of all connected blocks of shaded cells, in any order.

Or see the instruction booklet.