% heyawake 28 by ?, http://www.janko.at/Raetsel/Heyawake/028.a.htm
heyawake
very hard
17 17
+---+---+---+---+-----+---+---+---+
|0..|...|1..|1..|1....|1..|1..|...|
|...|...|...|...|.....|...|...|...|
|...|...|...|...|.....|...|...|...|
+---+-+-+---+...+---+-+---+...+---+
|2....|2....|...|...|.....|...|...|
|.....|.....+---+...|.....+---+...|
|.....|.....|1..|...|.....|1..|...|
+---+-+-+---+...+-+-+-+---+...+---+
|...|...|...|...|0|...|2..|...|...|
|...|...|...|...|.|...|...|...|...|
|...|...|...|...|.|...|...|...|...|
+---+...+---+-+-+-+...+---+-+-+---+
|...|...|1....|1..|...|.....|1....|
|...+---+.....|...+---+.....|.....|
|...|1..|.....|...|2..|.....|.....|
|...|...+---+-+-+-+...+---+-+-+---+
|...|...|...|...|.|...|...|1..|...|
+---+-+-+---+...+-+-+-+---+...|...|
|.....|1....|...|2..|.....|...|...|
|.....|.....+---+...|.....+---+...|
|.....|.....|3..|...|.....|0..|...|
+---+-+-+---+...+-+-+-+---+...+---+
|...|3..|...|...|.|...|1..|...|2..|
|...|...|...|...|.|...|...|...|...|
|...|...|...|...|.|...|...|...|...|
+---+...+---+-+-+-+...+---+-+-+---+
|...|...|.....|2..|...|1....|.....|
|...+---+.....|...+---+.....|.....|
|...|1..|.....|...|1..|.....|.....|
+---+...+---+-+---+...+---+-+-+---+
|1..|...|2..|2....|...|2..|1..|0..|
|...|...|...|.....|...|...|...|...|
|...|...|...|.....|...|...|...|...|
+---+---+---+-----+---+---+---+---+
