Living under attack in a one-dimensional virtual world

We present a kinematics problem in the framework of a videogame. Students are asked to find possible extensions of a safety zone on the x -axis to the right of an indestructible defense wall of height h placed at x = d in which the point-like balls, fired by strange attackers from the origin O of an Oxy reference system, cannot fall. We solve this problem analytically and suggest generalizations. This exercise may be appealing to students who play videogames, since it is proposed by recalling typical situations in simple virtual reality.