Picture logic puzzles in which cells in a grid must be colored or left blank according to numbers at the side of the grid to reveal a hidden picture. The numbers are a form of discrete tomography that measures how many unbroken lines of filled-in squares there are in any given row or column. nonogram, picture puzzle, logic puzzle, discrete tomography, grid puzzle, brain teaser, visual puzzle, online puzzle, 1000 piece, relaxing puzzle, mental workout, challenging puzzles, number puzzle, hidden picture, casual puzzle, animal, boys, puzzle game