from typing import List


def define_frontal_base_direction(robot: str) -> List:
    """Define the robot-specific frontal base direction in the base frame."""

    if robot != "iCubV2_5":
        raise Exception("Frontal base direction only defined for iCubV2_5.")

    # For iCubV2_5, the reversed x axis of the base frame is pointing forward
    frontal_base_direction = [-1, 0, 0]

    return frontal_base_direction