Star Battle

Star Battle is an object placement logic puzzle where solvers must place stars in a grid with marked regions. Each row, column, and region must have a specified number of stars. This number is dependent on the size of the grid, and is usually 2 stars for a 10x10 grid. Stars may not touch each other, even diagonally.

Background

Star Battle was invented by Hans Eendebak as a new genre debuting at the 2003 World Puzzle Championships.

Puzzle Application

TO DO

Strategy

• Small regions may admit only one or a few possible star configurations. It may be possible to divide regions into regions of size 2x2 or less, each of which may only contain at most one star as well.
• If you know that a star must be in one of two adjacent positions in a row, then you may rule out four squares having stars: the same row positions in the two adjacent columns. (And vice versa, swapping rows for columns.)
• If N regions, when taken together, span more than N rows or columns, then the additional squares cannot contain any stars.
• Conversely if N regions, when taken together, span less than N rows or columns, then the remaining squares cannot contain any stars.
• One interesting mathematical fact is that for a 4N x 4N grid, with N stars, there are only two solutions. (Incidentally, one of the 2003 WPC puzzles turned out to be this, which is understandable given that the theory had not been explored yet.)

Notable Examples

TO DO

See Also

• List of Star Battle puzzles