You vs a computer rider in a walled grid. Both leave solid trails — claim more space and make the opponent run out of room first.
You and a computer rider move one square per step across a walled grid, each leaving a solid trail. Tap anywhere to start the round; after that, tap the left half of the screen to turn 90° left and the right half to turn 90° right, relative to the way you are heading. Two quick taps are both used, one per step, so a double tap makes a tight U-shape.
Hitting any trail, a wall or a grey block destroys that rider instantly. You cannot reverse. On a desktop the arrow keys set an absolute direction instead.
If the computer crashes first you win the round (+10 points) and the next round starts on a fresh board. If you crash first the game is over. If both crash on the same step it is a tie: no points, and the same round is replayed.
Each round both riders get faster together, until round 10, when they move about fourteen squares per second. The computer also improves: in round 1 it wanders, from round 2 it counts open space, and from round 5 it judges which squares it can reach before you and blunders less every round. From round 4, grey blocks appear, placed as a mirror image for both sides, with more every round, so the arena keeps getting tighter and every run eventually ends.
Think in territory, not in chases. Once your trails split the board into separate regions, the rider with more open squares outlasts the other no matter how well either one turns. Use the opening steps to drive a long wall that divides the board in your favour, then seal the last gap the computer could use to reach your side.
The computer refuses to step into a square your head could enter on the next step, unless it has no other choice. That means charging straight at it rarely forces a crash or even a tie; it just swerves. Cut across the path it is heading along a few squares ahead of it instead, so its safe options shrink before it gets there.
Bank the easy rounds. In round 1 it wanders and boxes itself in, and from round 2 to 4 it only counts space near itself. From round 5 it weighs which squares it can reach before you, and its mistakes become rarer every round, so play the later rounds as careful space battles rather than gambles.
The grey blocks from round 4 onward are placed as a mirror image, so the pattern near your start matches the pattern near the computer's. Treat blocks as free walls: a block already closes half of a pocket. Inside your own region, fill the space in back-and-forth lanes so it stays in one piece, and remember that a quick double tap queues two turns, one per step, which is the fastest way to fold into a lane.