How it works
XO Shift is a variant of three men's morris — one of the oldest board games known, with boards scratched into temple roofs and city pavements thousands of years before tic-tac-toe existed in its modern form. It starts exactly like tic-tac-toe: you and a bot alternate placing marks on a 3×3 grid, and three in a row at any point during this Placement phase wins on the spot. The twist is what happens if nobody wins in six placements — the board doesn't fill up and stall, it enters a Movement phase where every mark is still in play.
In Movement, you no longer place new marks — you slide one of your existing three marks, on your turn, into an empty cell that's orthogonally or diagonally adjacent to it. That single rule turns a game that's a guaranteed draw with perfect tic-tac-toe play into a genuine contest of positioning and tempo, since a completed line can now be broken and rebuilt on a later turn. The one restriction: a piece that just slid somewhere can't immediately slide straight back to the cell it left — that lock is per piece and lifts the moment that specific piece moves again, so you can always free it up by moving it elsewhere first.
A round is a fixed best-of-3 against one bot difficulty: a win scores 10, a draw 5, a loss 0, averaged across all three games for a round score out of 10. A solo session plays three rounds at your chosen difficulty (9 games total); Daily and Friend Challenges run one round each against Easy, Medium and Hard in turn, with the bot dice and who moves first in every single game seeded from the challenge code, so everyone who opens the link faces an identically set-up bot.