/**
 * Pursuit steering - turn-rate-limited heading for chase sequences.
 *
 * Real fish don't beeline: a pursuing predator arcs onto its target and a
 * fleeing prey carves away. We model heading as a unit vector that rotates
 * toward the desired direction at a capped angular rate, so course changes
 * read as swimming, not teleport-aiming.
 */
export interface Heading {
    x: number;
    y: number;
}
/**
 * Rotates `current` (unit heading) toward `desired` (any non-zero vector),
 * clamping angular velocity to `maxTurnRate` rad/s. Returns a unit vector.
 */
export declare function steerHeading(current: Heading, desired: Heading, maxTurnRate: number, dt: number): Heading;
/**
 * Biases a flee direction back toward the screen interior so prey carves
 * along edges instead of bolting straight off-screen mid-chase.
 *
 * `margin` is the distance from each edge where the inward push starts;
 * the push ramps linearly to full strength at the edge itself.
 */
export declare function biasAwayFromEdges(direction: Heading, x: number, y: number, width: number, height: number, margin: number): Heading;
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