Find the path of a particle beam traveling through the grid.
The path enters and leaves the grid in the spots marked with arrows. It can travel in a straight line horizontally, vertically or diagonally, and in a grid point it can make a 90° turn. The path crosses itself diagonally in the spots marked with an ×, and it cannot cross itself anywhere else. Aside from this, each grid point is used at most once.
Some grid points are marked with a star. In these grid points the beam splits into two separate beams, from one diagonal beam into two horizontal/vertical beams or from one horizontal/vertical beam into two diagonal beams. See the figures below (rotations are possible). The beam cannot split anywhere else.
The numbers above and to the left of the grid indicate the number of beam segments crossing the respective row or column. The numbers below and to the right of the grid indicate how often the beam makes a 90° turn along the respective grid line, not counting the stars.
(Rules and example from WPC 2019 IB)
History of the puzzle
Invented by Jürgen Blume-Nienhaus (Germany) in 2011. First puzzle made by him is on LMD portal.
The name refers to an old colloquial term in physics.
In particle physics, the term particle zoo is used colloquially to describe a relatively extensive list of the then known "elementary particles" by comparison to the variety of species in a zoo.
In the history of particle physics, the situation was particularly confusing in the late 1960s. Before the discovery of quarks, hundreds of strongly interacting particles (hadrons) were known and believed to be distinct elementary particles in their own right. It was later discovered that they were not elementary particles, but rather composites of the quarks. The set of particles believed today to be elementary is known as the Standard Model and includes quarks, bosons and leptons.
Appearances in the past WPCs
- WPC 2019/Round 5 by Jürgen Blume-Nienhaus