The Day Thread Solves Star Battle

Star Battle is a puzzle that has consumed more of my recent hours than I would like to admit. Each puzzle consists of a square grid N units to a side, divided into N regions. In each row, column, and region of the grid, you must place X stars such that no two stars touch. It may sound simple, but the puzzle is anything but. I was introduced to it by the New York Times Puzzle Mania special section released this past December, which included an entire page devoted to it. Will Shortz, long-time NYT Crossword editor, wrote about them there:

“Every once in a while a puzzle comes along that gets me absolutely obsessed. KenKen did that to me when it first came out… The puzzle I can’t stop doing right now is one of pure logic called Star Battle – or, what I think is a better name for it, Two Not Touch. I came across it in Germany in October during the 28th World Puzzle Championship. I picked up a book there titled “Ratsel Dich Schlau und Glucklich” (roughly, Puzzling Yourself Clever and Happy”) that had a section of these… The Book’s puzzles come in three difficulty levels… At first i could barely do the easy ones. There were solving hints, but as I can’t read German, I had to figure everything out for myself.

Slowly, I discovered tricks and methods. When I finished my first medium-level Two Not Touch, I wrote in the margin, “Very satisfying!” The hard Two Not Touch puzzles remained utterly beyond me for a while. Really, I wondered, how does anyone do these? How do you even start?…

What I love about Two Not Touch is the simplicity of the instructions (just two sentences) and the elegance of the constructions.

Star Battle is free to play online at in sizes ranging from a 1-star 5×5 grid that can be knocked out in a few seconds to a massive 6-star 25×25 grid that releases special only once a month, to be chewed over repeatedly over the course of weeks. I’ve taken to doing the daily 4-Star puzzle (a 17×17 grid) every day the same way I do the NYT Crossword. If you’re in the market for a new time-waster (can’t imagine why), consider giving Star Battle a try.