Yiff! is a very addictive, original puzzle game for one or two players. The game is a variant of a little-known board game called Chain Reaction, which plays like a curious cross between Othello, Life, and Street Fighter: two players take turns placing foxes into "rooms" on a grid. After a certain number of foxes fill a room, they change color and scatter to adjoining rooms. The goal is to change all foxes to your own color. As you unleash bigger chain effects, a pair of Street Fighter–inspired "fox-morphs" battle it out at the bottom of the screen. Great idea, addictive gameplay. Puzzle lovers will definitely enjoy this obscure freeware gem. If you'd like a more straightforward PC version of Chain Reaction, check out the game with the same name on this site. Two thumbs up!Reviewed by: Underdogs