Hotaru Beam is played on a rectangular grid, usually of dashed lines, in which numbers in circles appear at some of the intersections on the grid. Additionally, each circle has a dot on one of the grid lines leading into the circle.
Rules (translated from Nikoli)
- Draw a line from each white circle's black dot to another white circle, following the grid's horizontal and vertical markings.
- Lines cannot be drawn from a black dot to another black dot, nor can they be drawn from a white circle not at its black dot to a white circle not at its black dot.
- No crossing or branching of lines is acceptable. At the end, the drawn lines will connect all white circles to form a single, contiguous network.
- The number on the white circle dictates how many times the line you draw from its black dot must bend before it meets another white circle.
A circle with 0 on it (not the same as a blank circle) is a given: It will have at least one line going straight in the direction of the dot until it hits another circle. Each circle will have a line coming out of it in the direction of the dot. Since turning at the corner of the grid counts as a turn, a 1 circle near the corner may be forced to simply continue along the edge of the grid.
- Nikoli's description of the puzzle (in Japanese), with example.