def cubic_dead_zone_func(dead_zone, expo_level):
    """
    Change input axis to be on "expo curve" with a dead zone. Makes the input somewhere
    between linear and cubic.

    Args:
        dead_zone (float, [0, 1)):  The amount of input for which there is 0 output.
        expo_level (float, [0, 1]): Interpolates between a linear and cubic curve. Cubic when
                                        expo_level is 0; linear when expo_level is 1.
    Returns:
        A function with a single argument (float, [-1, 1]) and output (float, [-1, 1])
    """

    def func(x):
        sgn = -1 if x < 0 else 1

        if abs(x) < dead_zone:
            return 0.
        scaled_x = sgn * (abs(x) - dead_zone) / (1. - dead_zone)

        return expo_level * scaled_x + (1. - expo_level) * pow(scaled_x, 3)

    return func
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