Dominoes, played with an ordinary double-six set against an opponent who actually thinks about it.
THREE WAYS TO PLAY, NOT ONE
Draw - the classic. Cannot go? Take tiles from the boneyard until you can.
Block - no boneyard. Cannot go, you pass, and a blocked hand goes to the lighter hand.
All Fives - score during play every time the two open ends add up to a multiple of five. A double standing crosswise counts both of its halves, so the 6-6 on the end is worth twelve.
AN OPPONENT WORTH BEATING
Three levels, and they differ in how they think, not in what they are allowed to see. The hard opponent watches what you pass on, works out which numbers you cannot hold, and quietly leaves both ends on exactly those numbers. It stops trusting that the moment you take a tile from the boneyard, because a tile you just drew was never covered by the pass.
TWO PLAYERS OR FOUR
Head to head, or a four-handed partnership game where you and your partner's scores combine.
BUILT TO BE PLAYED ON A PHONE
Opens straight onto a dealt board. No menu in the way, no Play button to find.
Tap a tile to pick it up, tap again to lay it. Never one careless tap.
Tiles you cannot play are dimmed and inert, so the rack tells you your options at a glance.
The board scales to fit whatever is on it, and a long chain folds into rows rather than running off the screen.
Your match is saved after every move. Close the app mid-hand and it is exactly where you left it.
OFFLINE, AND HONESTLY SO
No account, no sign-up, no server. Every game is played on your device against the computer, and your statistics never leave it. Statistics are kept per ruleset, because a win rate that averaged All Fives and Block together would describe neither.
In English, German, French and Italian.