Arrow keys or WASD · swipe on the board on a phone
You start with a small patch of ground. Drive out of it and you leave a trail behind you; drive back into your own ground and the loop closes, turning the trail and everything enclosed by it into yours. The bigger the loop, the bigger the prize — and the longer you are outside with a trail that anybody can cut. If a rival drives over your trail you are out, and the same is true in reverse, so clipping a rival mid-loop is the fastest way to take them off the board. Steer with the arrow keys or WASD, the on-screen pad, or by swiping the board. Claim 60% of the ground to win outright.
Your score is the largest share of the board you ever held, which means a huge loop you never close is worth nothing. Short, frequent loops beat one heroic sweep: you bank the ground and you are only exposed for a second at a time. Hug the edge of your own territory rather than cutting across open ground, because every step of trail is a step somebody can run into, and never cross your own trail — that kills you just as surely as a rival does. When a rival is out on a long loop, go and cut it; their whole territory is only dangerous while they are alive. Watch the corners, too: a loop that runs along the board edge encloses ground with half the trail, which is why the sides are worth more than the middle.