Nonogram pictures

The pictures drawn by the nonogram puzzles are derived from icon packs
released into the public domain (Creative Commons Zero, CC0 1.0). No
attribution is required; we credit them with thanks:

- Kenney (https://www.kenney.nl): 1-Bit Pack, Monochrome RPG, Tiny Dungeon,
  Tiny Town, Tiny Farm, Tiny Factory, Fish Pack, Board Game Icons,
  Game Icons.
- Nikoichu (https://nikoichu.itch.io/pixel-icons): 1-bit Pixel Icons.

CC0 1.0 Universal: https://creativecommons.org/publicdomain/zero/1.0/