Drag to spin the cube, pinch to zoom, tap a dot to place. Use the layer buttons along the right edge when an inner cell is hard to reach. Line up a full row matching the board size, 3 through 6, in any straight line through the cube: flat, tall, or diagonal.
3³ is the quick game: easy to learn, over in a couple of minutes, and the first player has a real edge. 4³ is the classic and the best balance of depth and pace, a good default for most matches. 5³ plays as a long strategic game, often two or three times the length of a 4³ match. 6³ is a marathon that can run past 200 moves, best saved for online games where moves wait for each player, and it is where the computer opponent is at its weakest.
A fair warning before starting big: the larger the cube, the longer the game and the smaller the dots, so lean on the layer buttons. Sizes beyond 6³ are not offered on purpose, since taps get too cramped and games stop being fun to finish.
P2P direct needs no setup: your phones talk to each other and the room lives only while its creator keeps the game open. Room server runs on this game's own server when it is hosted there: rooms survive closing the app, moves wait for slow opponents, and it works on strict networks.
Moves appear on both phones within about a second. After a game, both players tap Play again and the other side starts. Scores carry across rounds. If the guest drops, they can rejoin with the same code. If the creator leaves or their phone sleeps, the P2P room ends, so hosts should keep the screen awake. Codes never use the letters I, L, or O.
"Could not load the P2P library" means no internet when the game opened. "Room not found" means a typo or the host left. A join that hangs usually means a network that blocks peer connections, common on office and school WiFi. A phone hotspot usually fixes it, and the Room server mode is immune.