Designed to be impossible for a Deep Blue to beat the best human player but simple enough for a four year old to learn. Playable with a chess board and pieces but it’s not a chess variant. It’s Arimaa. (Pronounced a-ree-muh.) More importantly, it’s fun. Here’s how to play.
There’s more at the Arimaa site plus an app for Android and iOS. With the exception of the probably-not-going-to-be-reprinted-anytime-soon physical version, they’re all charmingly ugly. Don’t let that stop you.