Neutron

Neutron is a two-player abstract strategy board game played on a square board with a 5x5 grid.

Each player has five tokens of different colors that start on the baseline of the board closest to them. A single token of a third color called the Neutron starts in the center of the board. To win, either surround the Neutron or move it to your baseline. On a turn, a player does these two actions in this order:

1. Move the Neutron: Move it any direction to the furthest vacant square possible without leaping over other tokens; if you can't move it, you lose (because the other player has surrounded it).
2. Move one of your tokens: Move it any direction to the furthest square possible without leaping over other tokens.

On the first turn, the starting player skips the Neutron move.

Neutron was invented by Robert A. Kraus and first appeared in 1978. Bobail is nearly identical to Neutron, except in Bobail the Neutron can only move one vacant adjacent space. The publishers of Bobail claim that it's a traditional African game that pre-dates Neutron, but there is no evidence to back up this claim.