Spy is played on a 11x11 grid with 20 spaces designated as cities. There are five tiles in each of four colors, numbered 1-5, which are randomly placed on the cities at the start of the game.
Each player has four spies: one large, one medium, and two small. On a turn a player either places a spy on an empty edge space or move a spy any number of empty spaces orthogonally. A spy can end its move on a space with a smaller enemy spy, which is placed one space away in the direction the moving spy came from.
When four of the black tiles spaces are occupied those tiles are taken. The blue tiles are next, etc. The fifth tile in a color can be taken by any spy landing on its space.
When there is just one tile left the game ends. Players score the values of their tiles, plus a ten-point bonus for collecting three or four of the same number.