Poly-Y is an abstract board game for two players.
Install the app from the Google Play Store, or download an APK from the releases page.
Players take turns placing stones of their color on empty fields. Corners of the board can be captured by connecting the two adjacent sides with an arbitrary third side, creating a Y shape. The player that captures at least 3 of the 5 corners of the board wins.
In the example above, red has captured the top corner by connecting the adjacent top-left and top-right sides with the bottom side of the board. Meanwhile, blue has captured two corners on the left side of the board. Corner fields count as connecting to both adjacent sides, so blue's stones on the left connect three adjacent sides.
After the first player places his first stone, the second player may replace that stone with one of her own color (but only on her first turn!). This forces the first player to choose a first move that is neither too strong nor too weak.
Game description: https://boardgamegeek.com/boardgame/179816/poly-y
The version of the game uses a board with 5 sides and side length 7, as was used in the 2014 CodeCup: https://archive.codecup.nl/2014/
The AI is based on Lynx3 by Lesley Wevers & Steven te Brinke, which won the CodeCup: https://github.com/lwevers/lynx/