Coil is an asymmetrical but balanced 2-player connection game on a hexhex7 (or larger) board, where one player tries to form a loop of stones in his color, and the other tries to stop him.
There's a "chicken ballot" at the start to ensure that the two sides are balanced. Because loops come in a wide range of sizes and shapes, and have many degrees of freedom, the game has rich tactics and strategy.
Small loops threats force players to focus on local battles while large loop threats force them to think globally, and to consider how the local battles fit into the global war. Wise stone placements can contribute to the creation of multiple loops or to defense against multiple loops, leading to layered, multi-dimensional consequences for each turn.
See the rules of Coil here