Click cell to toggle between Shaded, Unshaded and Clear. Right click to Unshade/Clear
All the unshaded cells are in one continuous Cavity bordered by dark rock. Shade/unshade the cells to reveal the Cave.
Unshaded cells must be orthogonally connected. Shaded cells too, but only to the edge of the grid.
The clues are unshaded, and sum the unshaded cells in orthogonal directions until blocked by the edge or shaded cells.