Rules (as swiped from GM Puzzles): Either shade or add a single letter (A,B, or C) to each square so that each row and column contains exactly one A, one B, one C, and the rest shaded squares. Cells in the grid already marked with a letter can be shaded or remain unchanged.
Letters outside the grid indicate the first letter seen from that direction.
Numbers outside the grid describe the size of groups of consecutive shaded squares in that row or column in order. There must be at least one unshaded square between groups.