One step size per direction

You’re walking down a long, narrow valley in the fog (“Walk downhill”). Across the valley the ground is 100× steeper than along it, so plain steps of step_size × slope bounce from wall to wall while you crawl along the floor. Write steps(slopes_seen, step_size): slopes_seen has, for each direction, every slope you’ve felt so far, oldest first. Return the step to take now in each direction, using step_size as the biggest step you’d ever take.