Shade some cells in the grid such that all unshaded cells (the inside of the ‘cave’) are orthogonally connected to each other and all shaded cells (the walls) are orthogonally connected to the edge of the grid. Clue cells are unshaded and indicate the number of unshaded cells seen in the four orthogonal directions from that cell, including itself. Shaded cells obstruct vision. The cave and each wall section is a separate region for the purposes of a ‘LITS puzzle’. In a LITS puzzle, solvers must place one tetromino into each region. No two tetrominoes of the same shape may share an edge - reflections/rotations count as the same shape. All tetrominoes must form a single orthogonally connected area. No 2x2 area of the grid can be completely covered in tetrominoes. For the solution check function to work, having completed the puzzle, solvers should enter a 3 into every cell filled with a tetromino; a 2 into every non-tetromino shaded cell; and a 1 into every non-tetromino unshaded cell.