Fireball
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Haart has two snakes, not just one, and there's a good reason for it.
For simplicity, let's introduce a coordinate system with the origin in the top-left corner of the battlefield. The first number in a pair will represent the ordinate (from 1 to 11), and the second will represent the abscissa (from 1 to 15). The snakes move in the following sequence:
(11-4, 11-6); (def, 3-5); (11-15, 1-15); (11-4, 3-5); (7-15, 1-14); (11-6, 3-5); (11-15, 1-13); (11-6, 3-5); (9-15, 1-13).
The last two moves of the snakes form a cycle.
Malcolm managed to achieve a cycle with just one snake.