Free 2 player games you can play on one screen — lay the phone flat between you for a same-screen duel, or share the keyboard on desktop. All three games below also have a real CPU opponent, so a solo visitor isn't locked out either.
Paddle Clash — a fast neon air-hockey duel
Paddle Clash is a portrait-table air hockey duel, first to 7 goals. True simultaneous multi-touch means both players can strike at once on the same phone — P1 uses WASD on desktop, P2 the arrow keys.
Dots & Boxes 3D — the classic pen-and-paper game, rebuilt in 3D
Dots & Boxes 3D takes the game most people played on paper in school and rebuilds it as a real 3D board with glowing rails and brass pegs. Claim the third side of a box to score it and immediately go again — chains of boxes can swing a game in one turn.
Neon Four — connect four, with a CPU that actually plans
Neon Four is the drop-and-connect board game on a 7x6 grid: take turns dropping discs down a column and be the first to line up four across, down or diagonally. It's the easiest of the three to teach someone in one sentence, which makes it the natural pick when you're handing the phone to somebody who's never played anything here before. The CPU runs a real minimax search several moves deep rather than reacting only to your last disc, so it will both take a win you left open and block one you were setting up.
All three CPU opponents play real strategy rather than random moves, so solo practice against them is genuinely useful before you challenge a friend. Full list on the Multiplayer category page.