In the first post introducing the Genre Spotlight, I included this phrase:
"There may also be types that were common ten or twenty years ago but may not be so popular nowadays! (Remember, I'm a pandemic-era puzzler!)"
Three months in, there haven't really been any genres that would fall in this category. Coral is probably the first. It's been a staple of WPC rounds since 2001, yet doesn't seem to be quite as popular at the moment. (Perhaps it has been supplanted by Cross the Streams.) Genres with only outside clues are not my favorite, but the extra structure provided by the coral creates some interesting dynamics.
Rules: Shade some cells so that all shaded cells form one orthogonally connected area and the unshaded cells are all connected orthogonally by other unshaded cells to the edge of the grid. No 2x2 region may be entirely shaded. Clues outside the grid represent the lengths of each of the blocks of consecutive shaded cells in the corresponding row or column, not necessarily in order.