Hexopolis

From BoardGameGeek:

Hexopolis is a 2-player abstract competitive strategy game. Both players control a chip and place a collection of paths, walls, and cells to create an expanding, evolving board. Their objective is to destroy their opponent, which can be accomplished either by jumping on them from higher ground or surrounding them directly with 4 or more walls. The core mechanic of Hexopolis is "overriding", in which players can place one connector (a path or a wall) over another to redefine the logic of the board. -description from the designer